KR100691153B1 - Film bulk acoustic resonator - Google Patents

Abstract

The present invention relates to a thin film bulk acoustic resonator (FBAR), comprising a substrate, a lower electrode film formed on the substrate, a piezoelectric layer formed on the lower electrode film, and an upper electrode film formed on the piezoelectric layer, The lower electrode film is made of at least one material selected from the group consisting of Mo and W, the upper electrode film is provided with at least one material selected from the group consisting of Al, Au and Pt provides an FBAR device.

Film bulk acoustic resonators (FBAR), aluminum (Al), gold (Au), platinum (Pt)

Description

Thin Film Bulk Acoustic Resonator {FILM BULK ACOUSTIC RESONATOR}

1 shows an FBAR device according to one aspect of the present invention.

2 shows an FBAR device according to a specific embodiment of the present invention.

3 shows an FBAR device according to another aspect of the present invention.

<Code Description of Main Parts of Drawing>

11,21,31: substrate 12,22,32: membrane layer

14,24,34: lower electrode film 15,25,35: piezoelectric layer

16, 26, 36: upper electrode film

The present invention relates to a film bulk acoustic resonator, and more particularly, to a high quality FBAR device in which unnecessary energy loss is reduced by improving resistance of an electrode film.

As the recent communication technology is rapidly developed, the development of corresponding signal processing technology and radio frequency (RF) components is required. In particular, the high-frequency component technology, which is a hardware aspect, is being replaced by a thin film bulk acoustic wave resonator (TFR) according to the trend of miniaturization of mobile communication devices.

In general, a thin film bulk acoustic resonator (hereinafter referred to as an FBAR device) has a thin film basic structure having an upper and lower electrodes and a piezoelectric layer therebetween on a semiconductor substrate. In the FBAR device, when a voltage is applied to the upper and lower electrodes, a principle of converting a part of electrical energy into mechanical energy, which is acoustic waves, is used by the resonance characteristic of the piezoelectric layer. In addition, the FBAR device may have various types of isolation structures such as a Bragg reflector structure and an air gap structure at a position corresponding to the active region so that acoustic waves generated in the piezoelectric layer are not affected by the substrate. have.

The characteristics of the FBAR device may be determined by the piezoelectric layer and the upper and lower electrode films constituting the acoustic resonance unit. In particular, the piezoelectric properties of the piezoelectric layer and the electrical mechanical properties of the upper and lower electrode films are important factors for determining the Q value of the FBAR device.

In US Patent No. 5,587,620 (published date: December 24, 1996), in order to improve the characteristics of the FBAR device, the piezoelectric layer uses aluminum nitride (AlN) having excellent piezoelectric properties, and the upper and lower electrode films have molybdenum having high acoustic impedance. It is proposed to use (Mo) or tungsten (W).

However, although the molybdenum (Mo) or tungsten (W) as the electrode film material has excellent acoustic impedance characteristics, it has a disadvantage in that electrical loss is large because it has a relatively high electrical resistivity. In addition, since molybdenum (Mo) or tungsten (W) has a poor characteristic of being easily oxidized in the air, there is a disadvantage that an antioxidant layer is additionally required to prevent the frequency fluctuation due to oxidation.

As such, in the art, molybdenum (Mo) or tungsten (W) has been recognized as a limit to being advantageously used as an electrode film of an FBAR device due to its relatively high electrical resistivity and low oxidation resistance, despite excellent acoustic impedance characteristics. .

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide an FBAR device having improved electrical conductivity and / or oxidation resistance by improving the structure and material of the electrode film.

In order to realize the above technical problem, an aspect of the present invention includes a substrate, a lower electrode film formed on the substrate, a piezoelectric layer formed on the lower electrode film, and an upper electrode film formed on the piezoelectric layer. The lower electrode layer is formed of at least one material selected from the group consisting of Mo and W, and the upper electrode layer is formed of at least one material selected from the group consisting of Al, Au, and Pt. do.

The upper electrode film may include a plurality of layers made of different materials. In this case, the upper electrode film may include a first layer formed on the piezoelectric layer and a second layer formed on the first layer. The first layer may be made of at least one material selected from the group consisting of Al and Au, and the second layer may be made of Au or Pt.

Another aspect of the present invention includes a substrate, a lower electrode film formed on the substrate, a piezoelectric layer formed on the lower electrode film, and an upper electrode film formed on the piezoelectric layer, wherein the upper and lower electrode films At least one FBAR comprising a first layer of at least one material selected from the group consisting of Mo and W and a second layer of at least one material selected from the group consisting of Al, Au and Pt Provided is an element.

In a particular embodiment of the present invention, the lower electrode film includes the first and second layers, the second layer is formed on the substrate, and the first layer is formed on the second layer to form the piezoelectric body. Can touch the floor. In this case, the upper electrode film may be made of at least one material selected from the group consisting of Al, Au, and Pt. Further, the upper electrode film is formed on the piezoelectric layer and formed of at least one material selected from the group consisting of Al and Au, and at least one material formed on the lower layer and selected from the group consisting of Au and Pt. It may include an upper layer.

In another specific embodiment, the upper electrode film may include the first and second layers, the second layer may be formed on the piezoelectric layer, and the first layer may be formed on the second layer. In this case, the first layer of the upper electrode film may be made of at least one material selected from the group consisting of Au and Pt.

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

1 shows an FBAR device according to one aspect of the present invention.

Referring to FIG. 1, the FBAR device 10 according to the present embodiment includes a substrate 11 and a lower electrode film 14, a piezoelectric layer 15, and an upper electrode film 16 sequentially formed on the substrate 11. ). This embodiment is exemplified as an embodiment in which an air gap is employed as a means for separating the acoustic resonance unit and the substrate. That is, an air gap C is formed in the upper region of the substrate 11 corresponding to the active region in which the upper and lower electrode layers 16 and 14 and the piezoelectric layer 15 overlap each other. 12) has the structure provided.

In the present embodiment, the lower electrode film 14 is made of at least one material selected from the group consisting of Mo and W, and the upper electrode film 16 is at least one selected from the group consisting of Al, Au, and Pt. Made of matter. The lower electrode layer 14 may be formed of Mo or W in consideration of acoustic impedance characteristics, thereby selecting at least one of Al, Au, and Pt, which are excellent in the upper electrode layer 16, without significantly lowering a high Q value. Formation can greatly alleviate the reliability loss due to electrical losses and oxidation.

More specifically, Al and Au employed as the upper electrode film 16 of the present embodiment have higher electrical conductivity than Mo and W used as the lower electrode film 14, so that electrical losses can be reduced. In addition, in the case of Au and Pt, the oxidation resistance is superior to Mo and W used as the lower electrode layer 14, so that the reliability of unwanted frequency and characteristic changes can be greatly improved without an additional antioxidant layer. In this way, by forming the material of the upper electrode film 16 appropriately selected from Al, Au, and Pt, it is possible to increase the electrical conductivity and improve the oxidation resistance.

The upper electrode film 16 of the FBAR device 10 according to the present invention may be formed in a multilayer structure made of different materials selected from Al, Au, and Pt.

In such an embodiment, the upper electrode film can be more effectively improved in consideration of both the electrical conductivity side and the oxidation resistance side. FIG. 2 shows an FBAR device which improves electrical conductivity and oxidation resistance at the same time by employing a multilayered upper electrode film 26. As shown in FIG.

The FBAR device 20 shown in FIG. 2 includes a substrate 21 having an air gap C formed in one upper region similar to FIG. 1. The membrane layer 22 is formed on the substrate 21, and the lower electrode layer 24, the piezoelectric layer 25, and the upper electrode layer 26 are sequentially formed on the membrane layer 22.

The upper electrode film 26 according to the present embodiment is composed of a first layer 26a formed on the piezoelectric layer 25 and a second layer 26b formed on the first layer 26a. Since the second layer 26b is an exposed area, the second layer 26b is formed of Au or Pt having excellent oxidation resistance. In addition, the first layer 26a may be made of Al or Au having excellent electrical conductivity to compensate for electrical loss due to a lower electrode layer having a high specific resistance. In this way, the upper electrode film 26 is used as the multilayer structure 26a, 26b and formed of a metal material having appropriate characteristics according to the layer position, thereby providing excellent electrode film properties with excellent oxidation resistance as well as electrical conductivity. Can be.

In another aspect of the present invention, at least one electrode film of the upper and lower electrode films together with Mo and W having high acoustic impedance characteristics is formed of at least one metal material selected from Al, Au and Pt to maintain high Q characteristics while maintaining electrical characteristics. Provided is an FBAR structure that can improve conductivity and / or oxidation resistance. 3 shows such an FBAR device.

Similarly to the previous embodiments, the FBAR device 30 shown in FIG. 3 includes a substrate 31 having an air gap C formed in one upper region, and a membrane layer 32 is formed on the substrate 31. do. In addition, the FBAR device 30 includes a lower electrode film 34, a piezoelectric layer 35, and an upper electrode film 36 sequentially formed on the membrane layer 32.

The lower electrode film 34 according to the present embodiment is composed of a second layer 34b formed on the membrane layer 32 and a first layer 34a formed on the second layer 34b. The second layer 34b may be formed of at least one metal of Al, Au, and Pt, and preferably, Al or Au having excellent electrical conductivity. The first layer 34a is formed of Mo or W having excellent acoustic impedance as a layer in direct contact with the piezoelectric layer 35. In the structure of the lower electrode film 34, the electrical loss can be reduced through the second layer 34b having high electrical conductivity, and high Q value can be maintained through the first layer 34a having high acoustic impedance.

Similarly, the upper electrode film 36 according to the present embodiment is composed of a first layer 36a formed on the piezoelectric layer 34 and a second layer 36b formed on the first layer 36a. do. The first layer 36a in direct contact with the piezoelectric layer 35 is formed of Mo or W having excellent acoustic impedance. The second layer 36b may be formed of at least one metal of Al, Au, and Pt. Preferably, the second layer 36b is formed of Au or Pt having excellent oxidation resistance because it is an exposed area. More preferably, it can be formed of Au excellent in both oxidation resistance and electrical conductivity. In the structure of the upper electrode film 36, the electrical conductivity and / or the oxidation resistance can be improved through the second layer 36b while maintaining a high Q value through the first layer 34a having a high acoustic impedance.

In the embodiment shown in Fig. 3, for the upper and lower electrode films, a first layer made of at least one metal material selected from Mo and W, and a second layer made of at least one metal material selected from Al, Au, and Pt, Although the form employ | adopted was illustrated, this invention is not limited to this. That is, only one electrode of the upper electrode film and the lower electrode film can be formed in a multilayer structure according to the present invention, which can also be said to belong to the present invention.

In addition, the FBAR device shown in FIGS. 1 to 3 is an isolation structure of the substrate and the acoustic resonator unit. Although one embodiment of the structure is illustrated, the electrode film according to the present invention can be applied to an FBAR element employing another isolation structure.

For example, the present invention can use an etching cavity structure obtained by etching a substrate backside to form a cavity, and in various FBAR devices employing Bragg reflection structures obtained by alternately forming a plurality of layers having different acoustic impedance characteristics. It can be applied to prevent similar electric loss reduction effect and frequency fluctuation and characteristic degradation due to oxidation.

As such, the invention is not to be limited by the foregoing embodiments and the accompanying drawings, which are intended to be limited by the appended claims. Accordingly, various forms of substitution, modification, and alteration may be made by those skilled in the art without departing from the technical spirit of the present invention described in the claims, which are also within the scope of the present invention. something to do.

As described above, according to the present invention, the FBAR device is electrically replaced by partially replacing the metal material of the upper electrode film or the lower electrode film with at least one metal selected from Au, Al, and Pt having excellent electrical conductivity and / or oxidation resistance. Characteristic degradation due to loss and oxidation can be reduced. In particular, it is possible to provide a high quality FBAR device having excellent electrical conductivity and oxidation resistance by forming a structure of the upper / lower electrode film in a multilayer structure and employing a metal material having appropriate characteristics according to the position of each layer.

Claims (9)

delete delete delete Board; A lower electrode film formed on the substrate; A piezoelectric layer formed on the lower electrode film; And An upper electrode film formed on the piezoelectric layer, At least one of the upper and lower electrode films is formed of at least one material selected from the group consisting of Mo and W, and at least one selected from the group consisting of Al, Au, and Pt, the first layer of which one surface is in contact with the piezoelectric layer. An FBAR device comprising a second layer made of a material of and in contact with the other surface of the first layer. The method of claim 4, wherein The lower electrode film includes the first and second layers, And the second layer is formed on the substrate, and the first layer is formed on the second layer to be in contact with the piezoelectric layer. The method of claim 5, And the upper electrode film is formed of at least one material selected from the group consisting of Al, Au, and Pt. The method of claim 5, The upper electrode layer includes a lower layer formed on the piezoelectric layer and formed of at least one material selected from the group consisting of Al and Au, and an upper layer formed on the lower layer and formed of at least one material selected from the group consisting of Au and Pt. An FBAR device comprising a. The method according to claim 4 or 5, The upper electrode film includes the first and second layers, And the first layer is formed on the piezoelectric layer, and the second layer is formed on the first layer. The method of claim 8, And the second layer of the upper electrode layer is made of at least one material selected from the group consisting of Au and Pt.

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