KR20180102971A - Film bulk acoustic resonator and method for fabricating the same - Google Patents

Abstract

An embodiment of the present invention provides a film bulk acoustic resonator which includes: a substrate; a first electrode arranged on the upper side of the substrate; a piezoelectric body arranged on the first electrode and including AlN to which a dopant is added; and a second electrode arranged on the piezoelectric body and facing the first electrode while interposing the piezoelectric body. The dopant has 0.1 to 24 at% of Ta and 0.1 to 23 at% of Nb. Accordingly, the present invention can obtain piezoelectricity equal to or higher than the piezoelectricity in case of using rare earth metal as a dopant.

Description

FIELD OF THE INVENTION The present invention relates to a bulk acoustic resonator, and more particularly,

The present invention relates to a thin film bulk acoustic resonator and a method of manufacturing the same.

2. Description of the Related Art Demand for small and lightweight filters, oscillators, resonant elements, and acoustic resonant mass sensors used in such devices has been rapidly increasing due to recent rapid development of mobile communication devices, Is increasing.

A thin film bulk acoustic resonator (FBAR) is known as a means for implementing such a compact lightweight filter, an oscillator, a resonant element, and an acoustic resonance mass sensor.

FBARs can be mass-produced at a minimum cost and can be implemented in a very small size. In addition, it is possible to implement a high quality factor (Q) value, which is a major characteristic of a filter, and can be used in a microwave frequency band. Particularly, a PCS (Personal Communication System) and a DCS (Digital Cordless System) There is an advantage that it can be.

Generally, the FBAR has a structure including a resonator part formed by sequentially stacking a first electrode, a piezoelectric body, and a second electrode on a substrate.

The principle of operation of the FBAR is as follows. First, electric energy is applied to the first and second electrodes to induce an electric field in the piezoelectric layer. This electric field induces a piezoelectric phenomenon of the piezoelectric layer so that the resonator portion vibrates in a predetermined direction. As a result, a bulk acoustic wave is generated in the same direction as the vibration direction and resonance occurs

That is, the FBAR is an element using a bulk acoustic wave (BAW), and the effective electromechanical coupling coefficient (Kt2) of the piezoelectric body is increased, so that the frequency characteristics of the acoustic wave device are improved, .

Korean Patent Registration No. 10-0725010 Japanese Laid-Open Patent Publication No. 2009-100464 Japanese Laid-Open Patent Publication No. 2006-203304 Japanese Laid-Open Patent Publication No. 2015-198450 Japanese Laid-Open Patent Publication No. 2015-054986 Japanese Patent Publication No. 5957376 Japanese Patent Publication No. 5932168 Japanese Patent Publication No. 5190841 Japanese Patent Publication No. 5904591 U.S. Published Patent Application No. 2010-0283537

One of the objects of the present invention is to provide a piezoelectric body having piezoelectricity equal to or higher than that of a rare earth metal by forming a piezoelectric body of aluminum nitride by using a metal which is less expensive than rare earth metals and is lower in cost than rare earths as a dopant And to provide a thin film bulk acoustic resonator.

According to one aspect of the present invention, there is provided a thin film bulk acoustic resonator having a novel structure, and more particularly, a thin film bulk acoustic resonator according to an embodiment of the present invention includes a substrate; A first electrode disposed on the substrate; A piezoelectric layer disposed on the first electrode, the piezoelectric layer including AlN added with a dopant; And a second electrode disposed on the piezoelectric body and facing the first electrode with the piezoelectric material therebetween, wherein the dopant is 0.1 to 24 at% of Ta or 0.1 to 23 at% of Nb.

As a method for solving the above-mentioned problems, the present invention proposes a method of efficiently manufacturing a thin film bulk acoustic resonator of the above-described novel structure through another example, and more specifically, A method of manufacturing a thin film bulk acoustic resonator includes: providing a substrate; Forming a first electrode on top of the substrate; Forming a piezoelectric layer on the first electrode by sputtering a single target of AlNb containing 0.1 to 24 at% of Ta or 0.1 to 23 at% of Nb under a nitrogen atmosphere; And forming a second electrode on the piezoelectric body so as to face the first electrode with the piezoelectric body interposed therebetween.

The piezoelectric body of the thin film bulk acoustic resonator according to an embodiment of the present invention includes 0.1 to 24 at% of Ta or 0.1 to 23 at% of Nb as a dopant to be added to AlN, It can have piezoelectricity.

In addition, by using a single target, it is possible to overcome the unevenness of the composition of AlTaN or AlNbN.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURES 1A and 1B schematically illustrate cross-sectional views of a thin film bulk acoustic resonator in accordance with one embodiment of the present invention.
Fig. 2 schematically shows an enlarged view of A in Fig.
3 (a) schematically shows the elemental bond of aluminum nitride, and FIG. 3 (b) shows the case where the piezoelectric body of the thin film bulk acoustic resonator according to the embodiment of the present invention contains Ta or Nb as a dopant, Lt; RTI ID = 0.0 > dopant < / RTI >
4 and 5 are schematic circuit diagrams of a filter according to another embodiment of the present invention.
6 schematically shows a flowchart of a method of manufacturing a thin film bulk acoustic resonator according to still another embodiment of the present invention.
Fig. 7 schematically shows a state diagram of Al-Ta.
8 schematically shows a state diagram of Al-Nb.
9 schematically shows a single target sputtering apparatus used in a method of manufacturing a thin film bulk acoustic resonator.
10 (a) shows a crystal structure when a piezoelectric material is formed using a single target made of AlTa or a single target made of AlNb. FIG. 10 (b) To thereby measure the crystal structure of the piezoelectric body.

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

However, the embodiments of the present invention can be modified into various other forms, and the scope of the present invention is not limited to the following embodiments.

Further, the embodiments of the present invention are provided to more fully explain the present invention to those skilled in the art.

The shape and size of elements in the drawings may be exaggerated for clarity.

In the drawings, like reference numerals are used to designate like elements that are functionally equivalent to the same reference numerals in the drawings.

Thin film bulk acoustic resonator

Figures 1A and 1B schematically illustrate cross-sectional views of a thin film bulk acoustic resonator in accordance with an embodiment of the present invention, and Figure 2 schematically shows an enlarged view of Figure 1A.

First, the structure of a bulk acoustic resonator according to an embodiment of the present invention will be described with reference to FIG. 1A.

The acoustic resonator of the present invention may be a thin film bulk acoustic resonator and may include a substrate 110, an insulating layer 120, an air cavity 112, and a resonator 135.

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 substrate 110 from the resonator unit 135.

The insulating layer 120 may include at least one or a combination of silicon dioxide (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), aluminum oxide (Al ₂ O ₂ ), and aluminum nitride , But is not limited thereto. The insulating layer 120 may be formed on the substrate 110 by chemical vapor deposition, RF magnetron sputtering, or evaporation of the material.

An air cavity 112 may be disposed on the substrate 110. The air cavity 112 is positioned below the resonance part 135 so that the resonance part 135 can vibrate in a predetermined direction. The air cavity 112 may be formed by processing the membrane 130 through a predetermined process. The membrane 130 may function as a protective oxide layer or as a protective layer protecting the substrate 110. The membrane 130 may be formed of any one selected from the group consisting of SiO ₂ , Si ₃ N ₄ , AlN, Al ₂ O _3, and the like, or a combination thereof. Although not shown in FIG. 1A, a seed layer made of aluminum nitride (AlN) may be formed on the membrane 130. Specifically, a seed layer may be disposed between the membrane 130 and the first electrode 140. The seed layer may be formed using a dielectric or metal having an HCP structure in addition to AlN. In the case of a metal, for example, the seed layer may be formed of Ti.

In addition, an etch stop layer may be additionally formed on the insulating layer 120. The etch stop layer can protect the substrate 110 and the insulating layer 120 from the etch process to remove the sacrificial layer pattern and serve as a base for the deposition of various other layers on the etch stop layer.

The resonator 135 may include a first electrode 140, a piezoelectric body 150, and a second electrode 160. The first electrode 140, the piezoelectric body 150, and the second electrode 160 may be sequentially stacked.

The first electrode 140 is formed to extend from the upper portion of one region of the insulating layer 120 to the membrane 130 on the upper portion of the air cavity 112. The piezoelectric body 150 is formed on the first electrode 140 on the upper portion of the air cavity 112, And the second electrode 160 may be formed on the piezoelectric body 150 on the upper portion of the air cavity 112 from the upper portion of the other region of the insulating layer 120. The common areas overlapping in the vertical direction of the first electrode 140, the piezoelectric body 150, and the second electrode 160 may be located above the air cavity 112.

The resonator portion 135 may be partitioned into an active region and a non-active region. The active region of the resonator 135 vibrates in a predetermined direction due to a piezoelectric phenomenon occurring in the piezoelectric body 150 when electric energy such as a radio frequency signal is applied to the first electrode 140 and the second electrode 160 And corresponds to a region in which the first electrode 140, the piezoelectric body 150, and the second electrode 160 are superimposed in the vertical direction on the air cavity 112. The inactive region of the resonance portion 135 corresponds to a region outside the active region, which is a region which does not resonate due to the piezoelectric effect even if the first electrode 140 and the second electrode 160 are applied with electric energy.

Specifically, the resonance unit 135 generates a radio frequency signal having a resonance frequency corresponding to the vibration due to the piezoelectric development of the piezoelectric body 150. Specifically, the resonance unit 135 outputs a radio frequency signal having a specific frequency using a piezoelectric phenomenon, Can be output.

The passivation layer 170 may be disposed on the second electrode 160 of the resonator 135 to prevent the second electrode 160 from being exposed to the outside and oxidized, 140 and the second electrode 160 may be formed with an electrode pad 180 for applying an electrical signal.

The piezoelectric body 150 includes aluminum nitride (AlN) doped with a dopant, which is a part causing a piezoelectric effect to convert electrical energy into mechanical energy in an elastic wave form.

Conventionally, rare earth metals have been used as dopants. For example, rare earth metals which were used as dopants were one of scandium (Sc), erbium (Er), yttrium (Y), and lanthanum (La). However, rare earth metals are very expensive due to their rarity, which increases the overall manufacturing cost of the thin film bulk acoustic resonator.

Therefore, there is a need for other dopants that can improve the piezoelectricity and lower the manufacturing cost, as compared with the case of using a rare earth metal as a dopant.

1B is a cross-sectional view illustrating a volume acoustic resonator according to another embodiment of the present invention.

Referring to FIG. 1B, the volume acoustic resonator according to the embodiment of FIG. 1B is similar to the volume acoustic resonator according to the embodiment of FIG. 1A described above, so that the same or redundant description will be omitted and differences will be mainly described.

1B, the air cavity 112 is formed in a substantially trapezoidal shape and includes a first electrode 140 laminated on the membrane 130 by a height and a side angle of the air cavity 112, The second electrode 160 and the electrode pad 180 may be cracked and the crystals of the piezoelectric body 150 stacked on the membrane 130 may be abnormally grown. There may occur a problem that the insertion loss characteristic and the attenuation characteristic of the bulk acoustic resonator are deteriorated due to the abnormal crystal growth of the crack and the piezoelectric body 150.

1B, a volume acoustic resonator 100 according to an embodiment of the present invention includes a substrate 110, an air cavity 112, an insulating layer 120, a support 133, an auxiliary support 134, And may further include a protective layer 170 and an electrode pad 180. The protective layer 170 may be formed of a conductive material.

The upper surface of the substrate 110 may be provided with an insulating layer 120 that electrically isolates the resonant portion 135 from the substrate 110. The insulating layer 120 may further include an etch stop layer. The etch stop layer serves to protect the substrate 110 and the insulating layer 120 from the etching process and can serve as a base for depositing a plurality of layers or films on the etch stop layer.

The insulating layer 120 and the etch stop layer may be separated or the insulating layer 120 and the etch stop layer may be integrated into a single layer. In this case, the insulating layer 120 and the etch stop layer may be formed using an oxide layer.

The air cavity 112, the support portion 133, and the auxiliary support portion 134 may be formed on the etch stop layer.

The air cavity 112 is formed by forming a sacrificial layer on the etch stop layer and forming a pattern in which the support portion 133 is formed on the sacrificial layer and then forming the first electrode 140, ) And the like may be stacked, and then the sacrificial layer may be etched and removed. In one example, the sacrificial layer may comprise polycrystalline silicon (Poly-Si). The air cavity 112 may be positioned below the resonance unit so that the resonance unit 135 composed of the first electrode 140, the piezoelectric body 150 and the second electrode 160 can vibrate in a predetermined direction.

A support portion 133 and an auxiliary support portion 134 may be provided on the outer side of the air cavity 112. The thicknesses of the air cavity 112, the support portion 133, and the auxiliary support portion 134 formed on the etch stop layer may be the same. Accordingly, the one surface provided by the air cavity 112, the support portion 133, and the auxiliary support portion 134 can be substantially flat. According to the embodiment of the present invention, the resonance portion 135 is disposed on the flat surface from which the step is removed, so that the insertion loss and the attenuation characteristics of the volume acoustic resonator can be improved.

The cross section of the support portion 133 may have a substantially trapezoidal shape. Specifically, the width of the upper surface of the support portion 133 may be wider than the width of the lower surface, and the side connecting the upper surface and the lower surface may be inclined. The support 133 may be formed of a material that is not etched in the etching process for removing the sacrificial layer. In one example, the support 133 may be formed of the same material as the etch stop layer, and the support 133 may be formed of silicon dioxide (SiO ₂ ) and silicon nitride (Si ₃ N ₄ ).

The auxiliary support 134 may be provided on the opposite side of the air cavity 112 with respect to the outer-support portion 133 of the support portion 133. The auxiliary supporting portion 134 may be formed of the same material as the supporting portion 133 and may be formed of a different material from the supporting portion 133. For example, if the auxiliary support 134 is formed of a different material than the support 133, the auxiliary support 134 may correspond to a portion of the sacrificial layer formed on the etch stop layer that remains after the etching process .

FIG. 3 (b) is a schematic view showing an elemental bond of aluminum nitride, and FIG. 3 (b) is a cross-sectional view of a thin film bulk acoustic resonator according to an embodiment of the present invention when a piezoelectric body contains a dopant, As shown in FIG.

3 (a) and 3 (b), it can be seen that the net polarization is increased when a dopant having an element diameter larger than the element diameter of Al is added to AlN.

In addition, when a dopant having an element diameter larger than the element diameter of Al is added to the AlN, the lattice distortion becomes larger than when only pure AlN is used as the piezoelectric body. As a result, the ion displacement amount ionic displacement is increased to improve the piezoelectric characteristics of the piezoelectric body.

The following Table 1 shows the relationship between the nitrogen and the bond of various elements that can be used as a dopant of AlN used as a piezoelectric material of the thin film bulk acoustic resonator according to an embodiment of the present invention, the structure of nitride, It is the element diameter of the element.

Nitrogen and bonding ability The doping ability to aluminum nitride Structure of Nitride Elemental Diameter (Å) Ru ○ × - 1.34 Mo ○ × - 1.39 Ir △ × - 1.36 W ○ × - 1.39 Ta ○ ○ Rock Salt 1.46 Pt △ × - 1.39 Au ○ × - 1.44 Ni ○ ○ Nitrate 1.24 Cr ○ ○ Rock Salt 1.28 Cu ○ × - 1.28 Nb ○ ○ Rock Salt 1.46 V ○ ○ Rock Salt 1.34 Mn △ ○ Nitrate 1.27 Co △ ○ Nitrate 1.25 Zn ○ ○ Zn ₃ N ₂ Cubic 1.34 Re ○ ○ Re ₃ N HCP 1.37

Referring to Table 1, instead of the rare earth metal, an element that can be added as a dopant of a piezoelectric material including AlN is classified.

As shown in Figs. 3 (a) and 3 (b), in order to improve piezoelectricity of the piezoelectric body 150, the element diameter of the dopant to be added should be larger than 1.43 Å which is the element diameter of Al. That is, when the element diameter of the dopant is larger than the element diameter of Al, the net polarization is increased and the lattice distortion is increased. As a result, the ionic displacement is increased, Can be improved. It is also possible to bond with nitrogen and be doped into AlN.

It can be confirmed that Ta or Nb exists as an element that can bind to nitrogen among the various elements described in Table 1, can be doped into aluminum nitride, and at the same time has an element diameter larger than the element diameter of Al.

Accordingly, the thin film bulk acoustic resonator according to an embodiment of the present invention may include Ta or Nb as a dopant to be added to the piezoelectric 150 of AlN.

When the dopant is Ta, the piezoelectric body of the thin film bulk acoustic resonator according to an embodiment of the present invention may include AlN and AlTaN. When the dopant is Nb, the piezoelectric material of the thin film bulk acoustic resonator according to an embodiment of the present invention may include AlN and AlNbN.

In particular, the piezoelectric body 150 of the thin film bulk acoustic resonator according to an embodiment of the present invention can be formed by sputtering in a nitrogen atmosphere using a single target of AlTa or a single target of AlNb as described later, TaN or NbN, which is a factor for lowering the piezoelectricity, may not be contained in the piezoelectric substance.

Here, the absence of TaN or NbN in the piezoelectric body means that the piezoelectric body contains AlN and AlTaN only when the dopant is Ta, or the case where the piezoelectric body contains AlN and AlNbN when the dopant is Nb, It means that NbN does not exist in the piezoelectric body. Here, the error range refers to a range of levels at which impurities other than the target material are included in the piezoelectric process in a manufacturing process. For example, it may be the case that it is not detectable by XRD analysis of AlTaN or AlNbN doped with TaN or NbN.

The content of Ta contained in the piezoelectric body 150 may be 0.1 to 24 at%. When the content of Ta is less than 0.1 at%, the piezoelectricity hardly appears. Since the atomic weight of Ta is larger than that of Al, when the content of Ta exceeds 24 at%, a phase other than Al ₃ Ta is formed. That is, when the content of Ta exceeds 24 at%, there is a problem that the piezoelectric body 150 can not be formed uniformly when the piezoelectric body 150 is formed.

Further, when the atomic weight of Ta exceeds 13 at%, the content (wt%) of Ta contained in the piezoelectric substance 150 becomes larger than the content (wt%) of Al based on the wt% There is a problem that the piezoelectricity of the piezoelectric body 150 is reduced. That is, when the dopant is Ta, the content (wt%) of Ta contained in the piezoelectric body 150 may be smaller than the content (wt%) of Al contained in the piezoelectric body 150. Also, when the content (wt%) of Ta is larger than the content (wt%) of Al, problems such as phase separation of Al and Ta may occur during production of single target, which may result in difficulty in target production.

Accordingly, when the dopant added to the piezoelectric body 150 is Ta, the content of Ta is set to 0.1 to 24 at%, so that the piezoelectricity of the piezoelectric body 150 of the thin film bulk acoustic resonator Can be improved. More preferably, when the content of Ta is 0.1 to 13 at%, the characteristics of the piezoelectric substance 150 of the thin film bulk acoustic resonator can be improved stably.

The content of Nb contained in the piezoelectric body 150 may be 0.1 to 23 at%. When the content of Nb is less than 0.1 at%, almost no improvement in piezoelectric performance is observed. Since the atomic weight of Nb is larger than that of Al, when the content of Nb exceeds 23 at%, the content of Nb (wt%) and the content of Al (wt%) contained in the piezoelectric material are greater than the contents of wt% And thus NbN which does not affect the improvement of the piezoelectric property is formed, resulting in a problem that the piezoelectricity of the piezoelectric body 150 is reduced. That is, when the dopant is Nb, the content (wt%) of Nb contained in the piezoelectric body 150 may be smaller than the content (wt%) of Al contained in the piezoelectric body 150. Also, when the Nb content exceeds the Al content, problems such as phase separation of Al and Nb may occur during the manufacture of a single target, which may cause difficulties in target production.

Accordingly, when the dopant to be added to the piezoelectric body 150 is Nb, the thin film bulk acoustic resonator according to an embodiment of the present invention can reduce the piezoelectricity of the piezoelectric body 150 of the thin film bulk acoustic resonator by setting the content of Nb to 0.1 to 23 at% Can be improved.

In particular, the thin film bulk acoustic resonator according to an embodiment of the present invention may include only one element as a dopant to be added to the piezoelectric body 150.

When two or more dopants are used, it is difficult to adjust to a desired composition and the composition uniformity of the deposited thin film may be deteriorated. Further, there is a problem that it is difficult to manufacture a single target having an accurate and uniform composition even when a single target is prepared by incorporating two or more dopants.

The first electrode 140 and the second electrode 160 may include molybdenum (Mo) as the conductive metal. For example, the conductive metal included in the first electrode 140 and the second electrode 160 may be at least one selected from the group consisting of gold (Au), titanium (Ti), tantalum (Ta), molybdenum (Mo) And may be formed of one or an alloy of ruthenium (Ru), platinum (Pt), tungsten (W), aluminum (Al), nickel (Ni), and iridium (Ir).

Table 2 below shows the material consistency measured according to the electrode and the piezoelectric layer.

The first electrode The piezoelectric layer The second electrode Material consistency Comparative Example 1 Mo AlN Mo ○ Comparative Example 2 Mo AlTaN Mo × Example 1 MoTa AlTaN MoTa ◎ Example 2 MoNb AlTaN MoNb ○ Comparative Example 3 Mo AlNbN Mo × Example 3 MoNb AlNbN MoNb ◎ Example 4 MoTa AlNbN MoTa ○

Referring to Table 2, when Ta is added as a dopant to the piezoelectric body 150 (Examples 1 and 4), the first electrode 140 or the second electrode 160 may contain Ta or Nb as an additive element. have. In the case where Nb is added as a dopant to the piezoelectric substance 150 (Examples 2 and 3), the first electrode 140 or the second electrode 160 may include Nb or Ta as an additive element.

At this time, the content of Nb and Ta added to the first electrode 140 or the second electrode 160 is preferably 0.1 to 30 at% or less.

The first electrode 140 or the second electrode 160 includes a dopant included in the piezoelectric body 150 as an additive element so that the bonding property and the crystallinity according to the material matching property between the piezoelectric body 150 and the electrodes 140 and 160 The orientation can be increased.

The first electrode 140 or the second electrode 160 of the thin film bulk acoustic resonator according to an exemplary embodiment of the present invention may be formed of a piezoelectric material 150 ) May include an additional element (Examples 1 and 3).

filter

4 and 5 are schematic circuit diagrams of a filter according to another embodiment of the present invention.

Each of the plurality of volume acoustic resonators employed in the filters of Figs. 4 and 5 corresponds to the thin film bulk acoustic resonator shown in Fig. 1A or 1B.

Referring to FIG. 4, the filter 1000 according to another embodiment of the present invention may be formed of a ladder type filter structure. Specifically, the filter 1000 includes a plurality of thin film bulk acoustic resonators 1100 and 1200.

The first thin film bulk acoustic resonator 1200 may be connected in series between a signal input terminal to which the input signal RFin is input and a signal output terminal to which the output signal RFout is output and the second thin film bulk acoustic resonator 1200 may be connected in series, It is connected between the output stage and ground.

Referring to FIG. 5, the filter 2000 according to another embodiment of the present invention may be formed of a lattice type filter structure. Specifically, the filter 2000 includes a plurality of thin film bulk acoustic resonators 2100, 2200, 2300, 2400 to filter the balanced input signals RFin +, RFin- to produce balanced output signals RFout +, RFout- Can be output.

Manufacturing Method of Thin Film Bulk Acoustic Resonator

6 schematically shows a flowchart of a method of manufacturing a thin film bulk acoustic resonator according to another embodiment of the present invention.

For the sake of clarity, a method of manufacturing a thin film bulk acoustic resonator according to another embodiment of the present invention will be described with reference to FIGS. 1A and 2, focusing on the steps of forming an electrode and a piezoelectric body, A manufacturing method of a thin film bulk acoustic resonator which is conventionally used can be used.

Referring to FIG. 6, a method of fabricating a thin film bulk acoustic resonator according to another embodiment of the present invention includes a step S110 of forming a substrate, a step S120 of forming a first electrode on the substrate S120, (S130) of sputtering a single target of AlNb containing 0.1 to 24 at% of Ta or 0.1 to 23 at% of Nb containing 0.1 to 24 at% of Nb on the top of one electrode to form a piezoelectric body, And forming a second electrode so as to face the first electrode with the piezoelectric body interposed therebetween (S140).

First, a step of providing a substrate (S110) may be performed.

The substrate 110 may be composed of a silicon substrate. An insulating layer 120 is formed on the upper surface of the substrate 110 after the substrate 110 is provided to electrically isolate the substrate 110 from the resonator 135.

The insulating layer 120 may be formed by chemical vapor deposition (CVD) of at least one of silicon dioxide (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), aluminum oxide (Al ₂ O ₂ ), and aluminum nitride , RF Magnetron Sputtering (RF Magnetron Sputtering), and Evaporation (Evaporation).

After forming the insulating layer 120, the air cavity 112 can be formed. The air cavity 112 is positioned below the resonance part 135 so that the resonance part 135 can vibrate in a predetermined direction. The air cavity 112 is formed by forming an air cavity sacrificial layer pattern on the insulating layer 120 and then forming a membrane 130 on the air cavity sacrificial layer pattern and etching the air cavity sacrificial layer pattern by etching . The membrane 130 may function as a protective oxide layer or as a protective layer protecting the substrate 110. The membrane 130 may be formed of any one selected from the group consisting of SiO ₂ , Si ₃ N ₄ , AlN, Al ₂ O _3, and the like, or a combination thereof. Although not shown in FIG. 1A, a seed layer made of aluminum nitride (AlN) may be formed on the membrane 130. Specifically, a seed layer may be disposed between the membrane 130 and the first electrode 140. The seed layer may be formed using a dielectric or metal having an HCP structure in addition to AlN. In the case of a metal, for example, the seed layer may be formed of Ti.

Although not shown in FIG. 1A, an etch stop layer may be additionally formed on the insulating layer 120. The etch stop layer can protect the substrate 110 and the insulating layer 120 from the etch process to remove the sacrificial layer pattern and serve as a base for the deposition of various other layers on the etch stop layer.

After the step S110 of forming the substrate as described above, a step S120 of forming the first electrode 140 on the substrate 110 may be performed.

The first electrode 140 and the piezoelectric body 150 and the second electrode 160 to be described later may be formed by reactive sputtering using the sputtering apparatus shown in FIG.

The sputtering apparatus includes a chamber (11), a support member (12) and a target (13). A base member 14 serving as a base of a material to be grown is disposed on the upper portion of the support member 12. A material to be grown is deposited on the base member 14 as the sputtering process proceeds, 15) are grown. The atmosphere in the chamber 11 can be adjusted in the process of injecting argon (Ar) and nitrogen (N2) into the chamber 11 to grow the first electrode 140, the piezoelectric body 150 and the second electrode 160 have.

The step of forming the first electrode 140 (S120) may be performed using molybdenum (Mo) as the target 13 as the conductive metal. However, the present invention is not limited thereto. For example, a conductive metal such as gold (Au), titanium (Ti), tantalum (Ta), molybdenum (Mo), ruthenium (Ru), platinum (Pt), tungsten (Al), nickel (Ni), iridium (Ir), or an alloy thereof.

In addition, the first electrode 140 further includes Ta or Nb as an additive element, so that the material matching property with the piezoelectric substance 150 described later can be improved. Thus, it is possible to prevent the formation of abnormal crystals or the like in the piezoelectric body 150 in the step S130 of forming the piezoelectric body 150 to be described later, so that the piezoelectric characteristics can be formed.

In addition, MoTa and MoNb have a surface oxidation inhibition effect compared to pure Mo, so that an oxide film (MoO _x ) is not formed well. As a result, the crystal orientation can be improved in the piezoelectric body forming step.

Particularly, when the piezoelectric body 150 described later is formed as an AlTa single target, the first electrode 140 also includes Ta, and when the piezoelectric body 150 is formed of an AlNb single target, The one electrode 140 also includes Nb, so that the material matching between the piezoelectric substance 150 and the first electrode 140 can be remarkably improved.

Next, a step S130 of forming the piezoelectric body 150 on the first electrode 140 is performed.

As described above, the piezoelectric body 150 can be formed by reactive sputtering using the sputtering apparatus shown in FIG.

In particular, the step of forming the piezoelectric body 150 (S130) uses a single target as the target 13. The single target means that one target 13 contains all the elements to be formed in the forming layer 15.

The thin film bulk acoustic resonator of the present invention includes Ta or Nb as a dopant added to the piezoelectric material 150 of AlN. For this purpose, the single target uses AlTa or AlNb.

The AlTa single target or AlNb single target can be manufactured by the melting method or by the powder sintering method.

At this time, when an AlTa single target is used, the content of Ta contained in the single target is 0.1 to 24 at%. It can be seen that a single Al ₃ Ta phase is formed when the content of Ta in the AlTa single target is 0.1 to 24 at% (see FIG. 7 a). That is, when the content of Ta contained in the single target is in the range of 0.1 to 24 at%, a single target having a single phase can be provided, and a piezoelectric material having a uniform composition can be obtained by forming the piezoelectric material with a single- .

That is, since a single Al ₃ Ta phase is formed when the content of Ta in the AlTa single target is 0.1 to 24 at%, AlN and AlTaN can be uniformly formed in the process of growing the piezoelectric material 150. When the content of Ta is less than 0.1 at%, the improvement of the piezoelectric properties of the piezoelectric material 150 is insignificant. When the content of Ta exceeds 24 at%, the AlTa single target is not a single Al ₃ Ta phase, TaN is formed in the growth process, and the piezoelectric properties can be rather reduced. Therefore, when the content of Ta in the AlTa single target satisfies 0.1 to 24 at%, the uniformity in the growth of the piezoelectric body 150 can be improved and the piezoelectric characteristics of the thin film bulk acoustic resonator can be improved.

If the content of Ta exceeds 13 at%, the content (wt%) of Ta contained in the piezoelectric material 150 is the content (wt%) of Al based on the wt%, because the atomic weight of Ta is larger than that of Al. TaN that does not affect the improvement in piezoelectric performance may be formed, and the piezoelectricity of the piezoelectric body 150 may be reduced. Therefore, more preferably, when the content of Ta is 0.1 to 13 at%, the characteristics of the piezoelectric substance 150 of the thin film bulk acoustic resonator can be improved stably.

Referring to the Al-Nb state diagram of FIG. 7, it can be seen that a single Al ₃ Nb phase is formed when the content of Nb in the AlNb single target is 0.1 to 23 at% (see FIG. 8 b). That is, since a single Al ₃ Nb phase is formed when the content of Nb in the AlNb single target is 0.1 to 23 at%, AlN and AlNbN can be uniformly formed in the process of growing the piezoelectric material 150. When the content of Nb is less than 0.1 at%, the improvement of the piezoelectric characteristics of the piezoelectric material 150 is insignificant. When the content of Nb exceeds 23 at%, the AlNb single target is not a single Al ₃ Nb phase, NbN is formed in the growth process, so that the piezoelectric properties can be reduced. In particular, when the content of Nb exceeds 23 at%, the content (wt%) of Nb contained in the piezoelectric material 150 is less than the content (wt%) of Al based on the wt% NbN that does not affect the improvement in piezoelectric performance may be formed, and thus the piezoelectricity of the piezoelectric body 150 may be reduced.

Therefore, when the content of Nb in the AlNb single target satisfies 0.1 to 23 at%, the uniformity in the growth of the piezoelectric body 150 can be improved and the piezoelectric characteristics of the thin film bulk acoustic resonator can be improved.

The AlTa single target or AlNb single target thus manufactured can be placed on the target 13 of the sputtering apparatus of Fig. 9 and then grown under a nitrogen atmosphere to form the piezoelectric body 150. [

10 (a) shows a crystal structure when a piezoelectric material is formed using a single target made of AlTa or a single target made of AlNb. FIG. 10 (b) To thereby measure the crystal structure of the piezoelectric body.

10 (a) and 10 (b), when a piezoelectric material is formed using a dual target of Al and Ta or a dual target of Al and Nb, not only hexagonal structure but also cubic ) Structure can be observed. Such a cubic structure does not have piezoelectricity, which causes the piezoelectric properties of the piezoelectric material to be reduced.

However, since the method of manufacturing a thin film bulk acoustic resonator according to another embodiment of the present invention uses a single target of AlTa or a single target of AlNb to form a piezoelectric body, the formation of a cubic structure outside an error range is prevented, The characteristics can be improved.

Finally, a step S140 of forming the second electrode 160 on the piezoelectric body 150 may be performed.

The second electrode 160 may be formed by reactive sputtering using the sputtering apparatus shown in FIG.

Step S140 of forming the second electrode 160 may be performed using molybdenum (Mo) as the target 13 as the conductive metal. However, the present invention is not limited thereto. For example, a conductive metal such as gold (Au), titanium (Ti), tantalum (Ta), molybdenum (Mo), ruthenium (Ru), platinum (Pt), tungsten (Al), nickel (Ni), iridium (Ir), or an alloy thereof.

In addition, the second electrode 160 further includes Ta or Nb as an additional element, so that the material matching property with the piezoelectric substance 150 can be improved. Accordingly, the second electrode 160 can be more uniformly formed to improve the piezoelectric characteristics of the film bulk acoustic resonator.

Particularly, when the piezoelectric body 150 is formed as an AlNa single target, the second electrode 160 includes Ta, and the second electrode 160 includes Ta. When the piezoelectric body 150 is formed as an AlNb single target, (160) also includes Nb, so that the material matching between the piezoelectric body (150) and the second electrode (160) can be remarkably improved.

After that, the protective layer 170 and the electrode pads 180 are appropriately formed to complete the film thin film acoustic resonator.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

It will be apparent to those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. something to do.

110: substrate
112: air cavity
120: insulating layer
130: Membrane
135:
140: first electrode
150:
160: Second electrode
170: protective layer
180: Electrode pad
1000, 2000: filter
1100, 1200, 2100, 2200, 2300, 2400: thin film bulk acoustic resonator

Claims (12)

Board;
A first electrode disposed on the substrate;
A piezoelectric layer disposed on the first electrode, the piezoelectric layer including AlN added with a dopant; And
And a second electrode disposed on the piezoelectric body and facing the first electrode with the piezoelectric body interposed therebetween,
Wherein the dopant is 0.1 to 24 at% Ta or 0.1 to 23 at% Nb.
The method according to claim 1,
Wherein the content (wt%) of Ta or Nb is smaller than the content (wt%) of Al contained in the piezoelectric body.
The method according to claim 1,
When the dopant is Ta, the piezoelectric material includes AlN and AlTaN,
Wherein when the dopant is Nb, the piezoelectric body comprises AlN and AlNbN.
The method according to claim 1,
Wherein the piezoelectric body does not contain TaN or NbN.
The method according to claim 1,
Wherein the first electrode or the second electrode includes a conductive metal and an additive element, and the additive element includes Ta or Nb.
6. The method of claim 5,
Wherein the first electrode or the second electrode includes the same element as the dopant included in the piezoelectric body as an additive element.
Providing a substrate;
Forming a first electrode on the substrate;
Forming a piezoelectric layer on the first electrode by sputtering a single target of AlNb containing 0.1 to 24 at% of Ta or 0.1 to 23 at% of Nb under a nitrogen atmosphere; And
And forming a second electrode on the piezoelectric body so as to face the first electrode with the piezoelectric body interposed therebetween.
8. The method of claim 7,
Wherein the content (wt%) of Ta or Nb contained in the single target is smaller than the content (wt%) of Al contained in the single target.
8. The method of claim 7,
When the single target is AlTa, the piezoelectric material includes AlN and AlTaN,
Wherein when the single target is AlNb, the piezoelectric body includes AlN and AlNbN.
8. The method of claim 7,
Wherein the piezoelectric body does not contain TaN or NbN. 8. The method of claim 7,
In the step of forming the first electrode or the second electrode,
Wherein the first electrode or the second electrode includes a conductive metal and an additive element, and the additive element includes Ta or Nb.
12. The method of claim 11,
In the step of forming the first electrode or the second electrode,
Wherein the first electrode or the second electrode includes Ta when the single target is AlTa,
Wherein the first electrode or the second electrode includes Nb when the single target is AlNb.

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