KR20070020563A - Piezoelectric filter - Google Patents

Abstract

An object of the present invention is to provide a piezoelectric filter which can be miniaturized further.

According to the structure of this invention, the piezoelectric filter 10 has the 1st board | substrate 22 in which the at least 1st piezoelectric resonator 25 was formed in the main surface, and at least 1 in the main surface. The first substrate 12 in which two second piezoelectric resonators 15 are formed, and the main surface of the first substrate 22 and the main surface of the second substrate 12 face each other. Between the 22 and the second substrate 12, it extends around the first piezoelectric resonator 25 and the second piezoelectric resonator 15, the first piezoelectric resonator 25 and the first The piezoelectric resonator 15 is formed on the main surface of the first substrate 22 and the bonding pattern 20 for encapsulating the piezoelectric resonator 15 at an interval, and electrically connected to the first piezoelectric resonator 25. And a bonding layer 24x formed on the connected pad 28x and the pad 18x formed on the main surface of the second substrate 12 and electrically connected to the second piezoelectric resonator 15.

Piezoelectric Filters, Substrates, Parallel Resonators, Series Resonators, Pads, Junction Patterns

Description

Piezoelectric Filters {PIEZOELECTRIC FILTER}

The present invention relates to a piezoelectric filter.

BACKGROUND ART Miniaturization of piezoelectric filters including thin film piezoelectric resonators (BAW resonators) using the thickness vibration of piezoelectric thin films and surface acoustic wave resonators (SAW resonators) using surface acoustic waves has been progressing in recent years.

For example, Patent Document 1 proposes that a lid of the same size as the substrate on which the resonator element is formed is attached to both surfaces of the substrate to reduce the size of the package. In addition, Patent Literature 2 proposes a configuration in which two substrates on which a resonator element is formed are formed in parallel with a gap formed by a protrusion on a case.

Patent Document 1: Japanese Patent Publication No. 2004-503164

Patent Document 2: Japanese Patent Application Laid-Open No. 2002-43890

With miniaturization of mobile phones and the like in which piezoelectric filters are used, it is desired to make the piezoelectric filters even smaller.

However, in the structure disclosed by patent document 1, a package size cannot be made smaller than a board | substrate. In the substrate, at least two or more resonators of the series resonator and the parallel resonator must be formed on the same plane, and since many resonators are formed on the same plane, there is a limit to miniaturization of the substrate itself. In addition, since the series resonator and the parallel resonator are formed on the same plane, it is difficult to perform weight removal or addition separately in parallel by ion milling, sputtering, or the like. In addition, since a plurality of resonators are arranged in a plane, wiring resistance between the resonators increases, which leads to deterioration of filter characteristics. In addition, when it is desired to use a plurality of materials and vibration modes of the resonator, the material may be restricted or the process may be complicated, resulting in high cost. Moreover, since the lid which protects the resonator element formed in the board | substrate is provided, size becomes large and the material cost, processing cost, etc. of a lid are also needed.

In the structure disclosed in Patent Literature 2, the area can be reduced by overlapping two substrates with each other, but the area is larger than the substrate because the case is surrounded by the case. Moreover, since the space | interval is formed between board | substrates by the protrusion base, and the upper and lower openings of the case which accommodated the board | substrate are sealed with a lid, height (dimension of the thickness direction of a board | substrate) becomes large.

In view of such circumstances, the present invention is to provide a piezoelectric filter that can be further miniaturized.

The present invention provides a piezoelectric filter configured as follows.

The piezoelectric filter includes a first substrate having at least one first piezoelectric resonator formed on a main surface thereof, a second substrate having at least one second piezoelectric resonator formed on the main surface thereof, and the first substrate formed thereon. The first piezoelectric resonator and the second piezoelectric resonance between the first substrate and the second substrate in a state where the main surface of the first substrate and the main surface of the second substrate are opposed to each other. A bonding pattern extending around the ruler and joining the first piezoelectric resonator and the second piezoelectric resonator at intervals, a pad formed on the main surface of the first substrate, and the second substrate A bonding layer for bonding predetermined pads formed on the main surface, and external electrodes connected to the predetermined pads formed on the main surface of the second substrate.

In the above configuration, two substrates are joined in a joining pattern, a vibration space is formed inside the joining pattern, and the piezoelectric resonator is allowed to vibrate freely. The piezoelectric resonator of one substrate and the piezoelectric resonator of the other substrate are electrically connected inside the bonding pattern by the bonding layer. The pad may be connected to the piezoelectric resonator of the substrate. It may also be independent of the piezoelectric resonator of the substrate.

According to the said structure, one board | substrate can mutually be used as a lid which covers the piezoelectric resonator of another board | substrate, and the package which accommodates a board | substrate, and the lid board which covers a board | substrate can be eliminated.

Preferably, the bonding pattern includes at least one of Au, Ag, Sn or Cu.

According to the said structure, a joining pattern can join (enclose) a board | substrate with a solder alloy. Since the solder alloy is formed (melted) at a temperature lower than the temperature adversely affecting the substrate or the piezoelectric resonator, the substrate can be bonded (sealed) without adversely affecting the substrate or the resonator.

Preferably, the said 1st board | substrate and the said 2nd board | substrate respectively have a GND pad, and said GND pads are bump-bonded.

According to the said structure, GND of each board | substrate is common and GND can be taken out from one board | substrate to the outside. In addition, the bonding pattern around the piezoelectric resonator is made conductive, and the bonding pattern can be drawn out to GND.

Preferably, a through hole is formed through the second substrate, one end of the through hole is electrically connected to the pad or the GND pad of the second substrate, and the other end of the through hole. (Iii) is electrically connected to the external electrode.

The wiring between the external electrode and the piezoelectric resonator can be shortened to reduce the size of the piezoelectric filter. In addition, heat generated by vibrating the piezoelectric resonator tends to radiate to the substrate, thereby improving the electric power resistance of the piezoelectric filter.

Preferably, the bonding pattern is connected to the GND pad, the GND pad is connected to the external electrode through the through hole, and the external electrode is connected to GND.

According to the above configuration, since the bonding pattern is connected to GND, the piezoelectric filter can be electrostatic shielded.

Preferably, the opening at one end of the through hole is covered by the pad or the GND pad.

According to the above configuration, the vibration space can be blocked from the outside.

Preferably, the first piezoelectric resonator and the second piezoelectric resonator are thin film piezoelectric resonators in which a piezoelectric thin film is disposed between a pair of opposing excitation electrodes.

According to the above configuration, the piezoelectric filter (BAW device) using the thin film piezoelectric resonator (BAW resonator) can be miniaturized.

Preferably, either the first resonator or the second resonator is a series resonator, and the other of the first resonator or the second resonator is a parallel resonator.

According to the above configuration, since the series resonator and the parallel resonator are formed on different substrates, the resonance frequency of the series resonator and the resonance frequency of the parallel resonator can be adjusted separately. Therefore, it is easy to manufacture piezoelectric filters having different resonance frequencies of the series resonator and the parallel resonator.

Preferably, the piezoelectric thin film of the first piezoelectric resonator and the piezoelectric thin film of the second piezoelectric resonator are formed of different materials.

Suitable piezoelectric materials can be used for the first piezoelectric resonator and the second piezoelectric resonator (for example, for series resonators and parallel resonators).

Preferably, the excitation electrode of the first piezoelectric resonator and the excitation electrode of the second piezoelectric resonator are formed of different materials.

Suitable electrode materials can be used for the first piezoelectric resonator and the second piezoelectric resonator (for example, for series resonators and parallel resonators).

Preferably, the first piezoelectric resonator and the second piezoelectric resonator include a frequency adjusting film having different materials.

Suitable frequency adjusting materials can be used for the first piezoelectric resonator and the second piezoelectric resonator (for example, for series resonators and parallel resonators).

Preferably, the first piezoelectric resonator and the second piezoelectric resonator vibrate in at least one vibration mode of a fundamental wave or an integer multiple of two or more, respectively, and the first piezoelectric resonator and the second piezoelectric resonator In piezoelectric resonators, the orders of the vibration modes are different.

Appropriate vibration modes can be used for the first piezoelectric resonator and the second piezoelectric resonator (for example, for series resonators and parallel resonators).

Preferably, the first piezoelectric resonator and the second piezoelectric resonator are SAW resonators using surface acoustic waves, and the first substrate and the second substrate are made of the same single crystal piezoelectric material.

Substrates having the same linear expansion coefficient can be easily bonded at the wafer level. In addition, since the lid substrate is used for the SAW resonator, the manufacturing cost can be reduced.

Preferably, the second piezoelectric resonator is a BAW resonator.

The second substrate of the BAW resonator is a Si substrate, so that it is easy to form through holes for drawing out the external electrodes. Problems such as cracks generated when forming through holes or external electrodes in the piezoelectric single crystal can be avoided.

Preferably, the thickness of the second substrate is smaller than the thickness of the first substrate.

According to the above structure, the through hole can be easily formed in the second substrate having a relatively small thickness.

Preferably, the thickness of the piezoelectric thin film of the parallel resonator is greater than the thickness of the piezoelectric thin film of the series resonator.

The frequency of the parallel resonator must be lower than the frequency of the series resonator. According to the above configuration, the deterioration of characteristics can be made smaller than the method of increasing the electrode film thickness or irradiating oxygen plasma to lower the frequency.

Preferably, the thickness of the insulating film of the first piezoelectric resonator is different from the thickness of the insulating film of the second piezoelectric resonator. Even if the frequency adjusting film is not formed, the frequency of the piezoelectric resonator can be changed.

Moreover, this invention provides the composite filter which used the piezoelectric filter of any one of said structures. In this case, a composite filter such as a duplexer and a multi band filter can be miniaturized.

Moreover, this invention provides the communication apparatus using the piezoelectric filter of any one said structure, or the composite filter of the said structure. In this case, the communication device can be miniaturized.

Effect of the Invention

The piezoelectric filter of the present invention can be further miniaturized.

1 is a perspective view of a piezoelectric filter. (Example 1)

FIG. 2 is a cross-sectional view taken along the line II-II of FIG. 1 (Example 1)

3 is a cross-sectional view taken along the line III-III of FIG. 1 (Example 1)

4 is a cross-sectional view taken along the line IV-IV of FIG. 1 (Example 1)

5 is a perspective view of one substrate. (Example 1)

FIG. 6 is a cross-sectional view taken along the line VI-V in FIG. 2 (Example 1)

7 is an enlarged cross-sectional view of the bonding layer. (Example 1)

8 is a circuit diagram of a piezoelectric filter. (Example 1)

9 is a perspective view of a piezoelectric filter. (Example 2)

FIG. 10 is a cross-sectional view taken along the line X-X of FIG. 11. (Example 2)

FIG. 11 is a cross-sectional view taken along the line XI-XI of FIG. 9 (Example 2)

FIG. 12 is a cross-sectional view taken along the line XII-XII in FIG. 9 (Example 2)

13 is a circuit diagram of a piezoelectric filter. (Example 2)

14 is a sectional view of a piezoelectric filter. (Example 3)

Fig. 15 is a sectional view of a piezoelectric filter. (Example 4)

Fig. 16 is a circuit diagram of the duplexer. (Example 5)

17 is a circuit diagram of a communication device. (Example 6)

18 is a sectional view of a piezoelectric filter. (Example 7)

19 is a sectional view of a piezoelectric filter. (Example 8)

20 is a sectional view of a piezoelectric filter. (Example 9)

<Description of the code>

10 piezoelectric filter 12 substrate

15: series resonator (BAW resonator, piezoelectric resonator)

18x: Pad (GND Pad) 20: Bonding Pattern

22: substrate 24x: bonding layer

25: parallel resonator (BAW resonator, piezoelectric resonator)

28x: pad (GND pad) 40: piezoelectric filter

42: substrate

45a to 45d: series resonators (BAW resonators, piezoelectric resonators)

50: bonding pattern 52: substrate

54s, 54t: bonding layer

55a to 55d: parallel resonators (BAW resonators, piezoelectric resonators)

60: piezoelectric filter 62: substrate

66: SAW resonator (piezoelectric resonator) 70: junction pattern

72: substrate 76: SAW resonator (piezoelectric resonator)

80: piezoelectric filter 82: substrate

86: BAW resonator (piezoelectric resonator) 90: junction pattern

92 substrate 96 SAW resonator (piezoelectric resonator)

100: duplexer 200: communication device

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described, referring an Example, FIG.

(Example 1) FIG. 1 is a perspective view of the piezoelectric filter 10 of Example 1, FIG. 2 is a cross-sectional view taken along the line II-II of FIG. 1, and FIG. 3 is a cut along the line III-III of FIG. 4 is a cross-sectional view taken along the line IV-IV of FIG. 1, FIG. 5 is a perspective view of one substrate 12, FIG. 6 is a cross-sectional view of the other substrate 22, and FIG. 7 is an enlarged view of the bonding layer. 8 is an electric circuit diagram of the piezoelectric filter 10.

As shown in FIG. 8, the piezoelectric filter 10 is a ladder filter which comprised the series resonator 15 and the parallel resonator 25 in L shape.

As shown in FIGS. 2-4, the board | substrate 12 in which the series resonator 15 was formed, and the board | substrate 22 in which the parallel resonator 25 was formed are made into the resonators 15 and 25, respectively. The main surfaces formed are opposed to each other, and the gaps are formed in the bonding pattern 20 to be joined to each other, and the resonators 15 and 25 are sealed in the vibration space 11.

That is, the electrodes 16 and 26, the piezoelectric thin films 17 and 27, and the electrodes 18 and 28 are laminated on the main surfaces of the substrates 12 and 22. The piezoelectric thin films 17 and 27 are sandwiched between the electrodes 16, 18, 26 and 28, and the portions separated from the substrates 12 and 22 become the resonators 15 and 25. The resonators 15 and 25 are thin film piezoelectric resonators (BAW resonators) that utilize the thickness vibration of the piezoelectric thin films 17 and 27. The resonators 15 and 25 may be resonators using double or more integer waves having an insulating film, and the fundamental waves of only the electrodes 16 and 26 / piezoelectric thin films 17 and 27 and the electrodes 18 and 28 may be used. The used resonator may be used.

In one substrate 12, through holes 13a to 13d penetrating the substrate 12 are formed, and one end of the through holes 13a to 13d is connected to the external electrodes 14a to 14d exposed to the outside. Connected. The other end of the through holes 13a to 13d is formed by the pads 16a, 18b, 16c, and 18d formed on a part of the electrodes 16 and 18, and together with the electrical connection, the through holes 13a to 13d. The opening of the other end is covered and the sealing of the vibration space 11 is hold | maintained.

As shown in Fig. 2, one terminal (electrode 16) of the series resonator 15 is electrically connected to an external electrode 14a which is an input terminal, and the other terminal (electrode 18) is an output terminal. It is electrically connected to the external electrode 14b. As shown in FIG. 3, between the pads 18x and 28x formed in one part of the electrodes 18 and 28 is bump-bonded by the columnar bonding layer 24x. Thus, one terminal (electrode 28) of the parallel resonator 25 is electrically connected to the other terminal (electrode 18) of the series resonator 15, that is, the external electrode 14b serving as an output terminal. do. As shown in FIG. 4, between the pads 26c and 26d formed on a part of the electrode 26 and the pads 16c and 18d on the substrate 12 side, the columnar bonding layers 24c and 24d are used. Bump joints. Thereby, the other terminal (electrode 26) of the parallel resonator 25 is electrically connected to the external electrodes 14c and 14d which are GND terminals.

It is preferable to make the thickness of the piezoelectric thin film 27 of the parallel resonator 25 larger than the thickness of the piezoelectric thin film 17 of the series resonator 15. The frequency of the parallel resonator 25 must be lower than the frequency of the series resonator 15. In order to lower the frequency, the deterioration of characteristics can be made smaller than the method of increasing the electrode film thickness or irradiating oxygen plasma. Can be.

As shown in FIG. 1, FIG. 5, and FIG. 6, the bonding pattern 20 extends over the perimeter along the periphery of the board | substrates 12 and 22, and surrounds the resonators 15 and 25. As shown in FIG. The bonding pattern 20 is electrically connected to the external electrodes 14c and 14d serving as GND terminals through the electrode 26. The bonding pattern may be electrically floating without being connected to the GND terminal.

Next, the manufacturing method of the piezoelectric filter 10 is demonstrated.

The piezoelectric filter 10 is formed by forming a plurality of respective structures on the substrate 12 and 22 sides on roughly different wafers, and dividing the wafers after joining them.

That is, the sacrificial layer is formed on the Si wafers of the substrates 12 and 22, and the resonators 15 and 25 of the electrodes 16 and 26, the piezoelectric thin films 17 and 27, and the electrodes 18 and 28 are formed thereon. After forming the structure, the sacrificial layer is removed. The electrodes 16, 26; 18, 28 deposit Al after depositing Ti for enhancing the adhesion. ZnO is sputtered as the piezoelectric thin films 17 and 27. In addition to Al, Au, Pt, Cu, etc. may be used for the electrodes 16, 26; 18, 28. In addition, AlN etc. may be used for the piezoelectric thin films 17 and 27 other than ZnO.

Instead of the resonators 15 and 25 floating on the substrates 12 and 22, a diaphragm formed by anisotropically etching the substrates 12 and 22 (as a constituent film, Al ₂ O ₃ , SiO ₂ , AlN film It is also possible to form the electrodes 16 and 26, the piezoelectric thin films 17 and 27, and the electrodes 18 and 28 on the substrate).

Moreover, the pattern (bonding layer) is formed in the one or both of the board | substrates 12 and 22 corresponding to the bonding layers 24c, 24d, and 24x and the bonding pattern 20. As shown in FIG. For example, as shown in FIG. 7, as the bonding layer 20a of the board | substrate 12 side, the adhesion layer 30 of Ti, the solder material layer 31 of Cu, the solder material layer 32 of Sn, Ti The adhesion layer 33 of and the surface protection layer 34 of Au are formed. As the bonding layer 20b on the substrate 22 side, the Ti adhesion layer 36 and the Cu solder material layer 35 are formed. Each thickness of the bonding layers 20a and 20b is about 6 mu m. The solder material layers 31, 32, and 35 form a thin film of Cu—Sn solder alloy by heating in the bonding step described later. What is necessary is just to form the joining layer of the material used as the adhesive agent at the time of bonding in one or both of the board | substrates 12 and 22. FIG. In the formation process of the bonding layer, a resist mask opened in a pattern (bonding layer) portion on a substrate is formed by photolithography, the metal film of the bonding layer is sequentially deposited, and the metal film portion attached to the resist is removed together with the resist. Thus, the electrode is formed by the remaining metal film portion. The lift off method may be used. In addition to the Cu-Sn-based, Au-Sn-based solder thin films, resins such as polyimide and epoxy can be used.

Further, through holes 13a to 13d and external electrodes 14a to 14d are formed in the wafer of one substrate 12. That is, a through hole is formed in the substrate 12 with a laser or the like, and a conductive film is formed between the inner and outer electrodes 14a through 14d through the through holes 13a through 13d by a plating film or a conductive filler. Secure.

Next, the resonators 15, 25, the bonding pattern 20, the bonding layer of the bonding layers 24c, 24d, 24x, the through holes 13a-13d, the external electrodes 14a-14d, etc. are formed separately. Wafers of one of the substrates 12 and 22 are bonded to each other with the main surfaces on which the resonators 15 and 25 are formed. That is, for each piezoelectric filter 10, the bonding pattern 20 is formed around the resonators 15, 25, and bump bonding is performed between the pads 16c, 18d, 18x; 26c, 26d, 28x. At this time, when using a Cu-Sn-based solder thin film for bonding, by pressing while applying a temperature of about 300 ℃, it is possible to hermetically seal the vibration space 11 inside the bonding pattern 50. Become.

Next, the bonded wafers are cut along the boundary of each piezoelectric device 10 by dicing, for example, and separated into individual pieces of the piezoelectric device 10.

On the other hand, after joining two wafers, the wafer of the substrate 12 is polished to be thinner than the wafer of the other substrate 22, and the lead-out of the through holes 13a to 13d and the external electrodes 14a to 14d is pulled out. It is also possible to form a negative structure.

The piezoelectric filter 10 configured as described above can reduce the size (area) to the same extent as the substrates 12 and 22. In addition, since the airtight sealing can be performed using the bonding pattern 20, and the resonator surface of the board | substrate 12 and 22 is not formed in the surface of the piezoelectric filter 10, a package, a lid board, etc. for protecting a resonator This is unnecessary. Therefore, the piezoelectric filter 10 can be miniaturized more.

In addition, since the bonding between the resonators 15 and 25 is shortened, and electrical bonding in the longitudinal direction can be performed, the wiring resistance between the resonators can be reduced, and the filter characteristics are improved.

In addition, when the same kind of substrates are used, the coefficients of linear expansion are the same, so that bonding at the wafer level becomes easy. Do not select a substrate. When the resonators on the series side and the parallel side are manufactured on different substrates, frequency adjustments on the respective substrates can be precisely matched by performing frequency adjustment on each substrate.

(Example 2) FIG. 9 is a perspective view of the piezoelectric filter 40 of Example 2, FIG. 10 is a cross sectional view, FIG. 11 is a longitudinal sectional view cut along the line XI-XI of FIG. 9, FIG. 12 is a line XII of FIG. 13 is a circuit diagram of the piezoelectric filter 40. FIG.

As shown in FIG. 13, the piezoelectric filter 40 is a lattice filter which combined the series resonators 45a-45d and the parallel resonators 55a-55d in lattice form.

As shown in Figs. 9 to 12, the piezoelectric filter 40 is substantially the same as the first embodiment, with the substrate 42 on which four series resonators 45a to 45d are formed and four parallel resonators 55a to. The substrate 52 on which 55d is formed is formed so as to face each main surface on which the resonators 45a to 45d and 55a to 55d are formed to form a gap with the bonding pattern 50, and the resonators 45a to 45d are joined. 55a to 55d are sealed in the vibration space 41.

That is, electrodes 46a to 46d; 56a to 56d, piezoelectric thin films 47s and 47t; 57s and 57t, and electrodes 48s and 48t and 58s and 58t are stacked on the main surfaces of the substrates 42 and 52. Piezoelectric thin films 47s, 47t; 57s, 57t are sandwiched between the electrodes 46a-46d; 56a-56d and the electrodes 48s, 48t; 58s, 58t, and portions separated from the substrates 42, 52, Thin film piezoelectric resonators (BAW resonators) 45a to 45d; 55a to 55d.

Through-holes 43a to 43d, 43x, and 43y (not shown other than 43a and 43b in FIG. 11) are formed in one substrate 42, and as shown in FIG. 9, 6 is formed on the upper surface of the substrate 42. FIG. Four external electrodes 44a to 44d, 44x, 44y are exposed. The electrodes 46a to 46d are electrically connected to the external electrodes 44a to 44d, respectively, and the series resonators 45a and 45b are connected in series between the external electrodes 44a and 44b to connect the external electrodes 44c. And 44d), the series resonators 45c and 45d are connected in series. The external electrodes 44x and 44y are electrically connected to the bonding pattern 50.

Pads 46a'-46d '; 56a'-56d' (parts 46a ', 46b'; 56a ', 56b' in Fig. 11) formed on a portion of the electrodes 46a-46d; 56a-56d are not shown. Bump bonding is performed by the bonding layers 54a to 54d (not shown other than 54a and 54b in Fig. 11), so that one terminal (the electrodes 56a to 56d) of the resonators 45a to 45d is connected to the external electrodes 54a to 54b. 54d) respectively electrically.

In addition, the pads 48s ', 48t'; 58s ', 58t' (not shown other than 48t ', 58t' in Fig. 12) formed on a part of the electrodes 48s, 48t; 58s, 58t are bonded to the layer 54s. Bumping by 54t), the other terminals (electrodes 58s and 58t) of the resonators 55a to 55d are electrically connected to respective connection portions between the series resonators 45a and 45b and between 45c and 45d, respectively. Is connected.

When the lattice filter is formed on one substrate, the substrate becomes large and the wiring resistance also increases. Like the piezoelectric filter 40 of the second embodiment, when the circuit is three-dimensionally formed using the two substrates 42 and 52, the wiring is shortened, so that the filter characteristics can be improved.

(Example 3) FIG. 14 is a sectional view of a piezoelectric filter 60 of Example 3. FIG.

The piezoelectric filter 60 includes substrates 62 and 72 on which resonators (SAW resonators) 66 and 76 using surface acoustic waves are formed. That is, comb-shaped electrodes IDT are formed on the substrates 62 and 72 of the piezoelectric material. The external electrode 64, the bonding pattern 70, the bonding layer 74 and the like have the same configuration as in the other embodiments.

Conventionally, since the surface acoustic wave element uses a piezoelectric substrate having anisotropy in the coefficient of linear expansion, when the lid substrate is bonded at the wafer level, the surface piezoelectric substrate has no choice but to use the same piezoelectric substrate as the lid substrate. If an expensive piezoelectric substrate is used only as a simple structural material (lid substrate), it will cause a cost increase. Therefore, the surface acoustic wave device is packaged using a resin or the like having airtightness or low strength.

In the piezoelectric filter 60 of Example 3, since the board | substrates 62 and 72 which have the same linear expansion coefficient can also be used as a package, the piezoelectric filter 60 can be reduced in size and manufacturing cost can be reduced.

(Example 4) FIG. 15 is a sectional view of a piezoelectric filter 80 of Example 4. FIG.

The piezoelectric filter 80 combines the piezoelectric substrate 82 on which the BAW resonator 86 is formed, and the piezoelectric substrate 92 on which the SAW resonator 96 is formed. The external electrode 84, the bonding pattern 90, the bonding layer 94, and the like are configured in the same manner as in the other embodiments.

The external electrode 84 is preferably provided on the substrate 82 that forms the BAW resonator 86. Si may be used for the substrate 82 of the BAW resonator 86, and it is easy to form through holes, and is generated when the through holes and the external electrodes are formed in the piezoelectric single crystal substrate 92 of the SAW resonator 96. This is because a problem such as cracking can be avoided.

Embodiment 5 FIG. 16 is a circuit diagram of a duplexer 100 of Embodiment 5. FIG.

The duplexer 100 is provided with an antenna terminal 102, a receiving side terminal 104, and a transmitting side terminal 106. The duplexer 100 includes a piezoelectric filter that passes only the reception frequency band and attenuates the transmission frequency band between the reception side terminal 104 and the antenna terminal 102. Further, a piezoelectric filter is provided between the transmitting side terminal 106 and the antenna terminal 102 to pass only the transmission frequency band and attenuate the reception frequency band.

For example, similarly to the piezoelectric filters of the above embodiments, the duplexer 100 is formed by forming a receiving side filter piezoelectric resonator on one substrate and a transmitting side filter piezoelectric resonator on another substrate and joining two substrates together. Can be formed. In addition, you may form matching circuits, such as R and C, in each board | substrate. In addition, a resonator of a part of the receiving filter, a resonator of a part of the transmitting filter, and a matching circuit are formed on one substrate, and a filter resonator and a matching circuit of the receiving or transmitting side are formed on the other substrate. Also good. As a result, the duplexer 100 can be downsized like the piezoelectric filter.

(Sixth Embodiment) Fig. 17 is a main block diagram of a communication device 200 of a sixth embodiment.

The communication device 200 can switch the reception frequency by the switch SW, corresponding to another system such as a multi-band mobile phone. The duplexer 202 is connected to the antenna 201. Two systems of receiving circuits are connected to the duplexer 202 via a switch SW. That is, between the switch SW and the piezoelectric filters 209 and 209a at the IF stage, the receiving RF piezoelectric filters 204 and 204a, the amplifiers 205 and 205a, and the receiving side mixers 203 and 203a, respectively. Connected. In addition, between the duplexer 202 and the mixer 206 on the transmission side, an amplifier 207 and a transmission side piezoelectric filter 208 constituting the RF stage are connected.

Piezoelectric filters 204, 204a, 208, 209, and 209a and duplexer 202 having the same configuration as the above embodiment are used. Moreover, you may use the RF filter module (multi-band filter) which modularized the circuit element containing at least the reception side RF piezoelectric filter 204 and 204a. As a result, the communication apparatus 200 can be miniaturized.

(Example 7) FIG. 18 is a sectional view of a piezoelectric filter 300 of Example 7. FIG. 18 is a cross-sectional view corresponding to FIG. 2 of the first embodiment.

A sacrificial layer pattern is formed on the substrate 302, and an insulating film 304, such as SiO ₂ , is formed by covering the sacrificial layer pattern. The thin film portion 310 sandwiching the piezoelectric thin film 306 between the pair of electrodes 305 and 307 is formed thereon. The insulating film 304 can be thickened to form a resonator using double or more integer doubles. The insulating film 304 can be thinned to form a resonator using a fundamental wave. For example, when ZnO is used for the sacrificial layer, the piezoelectric thin film 306 is protected because the insulating film 304 acts as an etch stop layer when etching the sacrificial layer with acid.

The thickness of the insulating film of the first piezoelectric resonator may be different from the thickness of the insulating film of the second piezoelectric resonator. The frequency of the piezoelectric resonator can be changed even without forming the frequency adjusting film.

(Example 8) FIG. 19 is a sectional view of a piezoelectric filter 400 of Example 8. FIG. 19 is a cross-sectional view corresponding to FIG. 2 of the first embodiment.

Unlike Example 1, the space | gap 403 opened in the upper surface side is formed, and the space | gap 403 does not penetrate the board | substrate 402. As shown in FIG. The space | gap 403 is formed by forming the etching resist which has an opening in the upper surface of the board | substrate 402, for example, and etching the board | substrate 402 from the opening.

The cavity 403 formed on the upper surface of the substrate 402 is filled with a sacrificial material and then planarized. After planarization, the electrode 405, the piezoelectric thin film 406, and the electrode 407 are laminated. Since one cavity 403 can be formed in one resonator, the area of the portion of the thin film portion 410 that has emerged from the substrate 402 becomes small, the thin film portion 410 is less likely to be broken, and the yield is improved. .

(Example 9) FIG. 20 is a sectional view of a piezoelectric filter 500 of Example 9. FIG. 20 is a cross-sectional view corresponding to FIG. 2 of Embodiment 1. FIG.

In the piezoelectric thin film resonator, the acoustic reflection layer 503 is formed on the substrate 502 instead of the cavity or the void, and the piezoelectric thin film 506 is disposed between the pair of electrodes 505 and 507 on the acoustic reflection layer 503. The sandwiched thin film portion 510 is formed. The acoustic reflection layer 503 acoustically separates the resonator from the substrate 502 so that vibration is not transmitted to the substrate 502.

Since the piezoelectric thin film resonator does not form voids or voids under the thin film portion 510, the piezoelectric thin film resonator has strength and is easy to manufacture.

In addition, this invention is not limited to each said Example, It can implement by making a various change.

For example, the types of the two substrates to be bonded may be different.

For example, in the case of a thin film piezoelectric filter (BAW filter), a substrate on which an optimized resonator is formed using ZnO as a piezoelectric body and a substrate on which an optimized resonator is formed using AlN as a piezoelectric body are attached to each other. By combining the characteristics of a ZnO resonator with a wider band but smaller Q and an AlN resonator with a narrower band but higher Q, a filter having both selectivity and wide bandwidth can be manufactured. Conventionally, it is difficult to fabricate resonators using two kinds of piezoelectric bodies on the same substrate. For example, when patterning ZnO, AlN may be damaged by an etchant, or the process may be complicated, resulting in a decrease in yield. Although there existed a problem, such as a different board | substrate, by using a different board | substrate, it is easy to manufacture the resonator containing a frequency adjusting film from which a material differs.

In the case of a surface acoustic wave filter (SAW filter), it is also possible to combine the piezoelectric substrate of LiTaO _{3 and} the piezoelectric substrate of LiNbO ₃ .

Or, the board | substrate which formed the resonator optimized using the fundamental wave structure, and the board | substrate optimized using the double wave structure are attached to each other. The fundamental wave resonator is wideband and high Q, but because of its low strength, it is difficult to form a large area resonator. In addition, the frequency temperature characteristic tends to deteriorate. On the other hand, in the double wave structure, the band is narrow and Q tends to be low. However, the frequency temperature characteristics can be reduced by combining the material with high strength, easy formation of a large-area resonator, and a negative temperature coefficient such as SiO ₂ . By combining these characteristics, it is possible to produce a filter that satisfies both separation, broadband, and low TCF (frequency temperature coefficient).

In general, fabricating a resonator using two types of structures on the same substrate is a complicated process and leads to a decrease in yield, but a relatively simple process of separately fabricating and joining substrates results in a decrease in yield. I can produce it without doing it.

Claims (19)

A first substrate having at least one first piezoelectric resonator formed on a main surface thereof; A second substrate having at least one second piezoelectric resonator formed on a main surface thereof; The first piezoelectric resonator and the second substrate between the first substrate and the second substrate in a state where the main surface of the first substrate and the main surface of the second substrate are opposed to each other. A bonding pattern extending around the piezoelectric resonator and joining the first piezoelectric resonator and the second piezoelectric resonator at intervals; A bonding layer for bonding a pad formed on the main surface of the first substrate and a predetermined pad formed on the main surface of the second substrate; And an external electrode connected to the predetermined pad formed on the main surface of the second substrate. The piezoelectric filter according to claim 1, wherein the bonding pattern contains at least one of Au, Ag, Sn, and Cu. The piezoelectric filter according to claim 1 or 2, wherein each of the first substrate and the second substrate includes a GND pad, and the GND pads are bump-bonded to each other. The through-hole which penetrates the said 2nd board | substrate is formed, The one end of the said through-hole is formed in the said pad or the GND pad of a said 2nd board | substrate. A piezoelectric filter, wherein the piezoelectric filter is electrically connected, and the other end of the through hole is electrically connected to an external electrode. The method of claim 1, wherein the bonding pattern is connected to the GND pad, the GND pad is connected to the external electrode through the through hole, and the external electrode is connected to GND. Piezoelectric filter, characterized in that. The piezoelectric filter according to any one of claims 1 to 5, wherein the opening of the one end of the through hole is covered by the pad or the GND pad. The piezoelectric resonator according to any one of claims 1 to 6, wherein the first piezoelectric resonator and the second piezoelectric resonator are thin film piezoelectric resonators having a piezoelectric thin film disposed between a pair of opposing excitation electrodes. Piezoelectric filter. 8. The method of claim 7, wherein either one of the first resonator or the second resonator is a series resonator, and the other of the first resonator or the second resonator is a parallel resonator. Piezoelectric filter. The piezoelectric filter according to claim 7 or 8, wherein the piezoelectric thin film of the first piezoelectric resonator and the piezoelectric thin film of the second piezoelectric resonator are formed of different materials. The piezoelectric filter according to claim 7, 8 or 9, wherein the excitation electrode of the first piezoelectric resonator and the excitation electrode of the second piezoelectric resonator are formed of different materials. The piezoelectric filter according to any one of claims 7 to 10, wherein the first piezoelectric resonator and the second piezoelectric resonator include a frequency adjusting film having a different material. The said 1st piezoelectric resonator and the said 2nd piezoelectric resonator vibrate in the at least 1 oscillation mode of a fundamental wave or 2 or more integer multiples, respectively, The piezoelectric filter of claim 1 and the second piezoelectric resonator have different orders of vibration mode. The said 1st piezoelectric resonator and the said 2nd piezoelectric resonator are SAW resonators using a surface acoustic wave, The said 1st board | substrate and the said 2nd board | substrate in any one of Claims 1-6. This piezoelectric filter is a board | substrate which consists of piezoelectric materials of the same single crystal. The piezoelectric filter according to any one of claims 1 to 6, wherein the second piezoelectric resonator is a BAW resonator. The piezoelectric filter according to any one of claims 1 to 14, wherein the thickness of the second substrate is smaller than the thickness of the first substrate. The piezoelectric filter according to any one of claims 8 to 10, wherein a thickness of the piezoelectric thin film of the parallel resonator is larger than a thickness of the piezoelectric thin film of the series resonator. The piezoelectric filter according to any one of claims 7 to 12, wherein the piezoelectric filter has an insulating film, and the thickness of the insulating film of the first piezoelectric resonator is different from that of the insulating film of the second piezoelectric resonator. The piezoelectric filter of any one of Claims 1-17 was used, The composite filter characterized by the above-mentioned. The piezoelectric filter of any one of Claims 1-17, or the composite filter of Claim 18 was used, The communication apparatus characterized by the above-mentioned.

Images