JP4570653B2 - Surface acoustic wave filter - Google Patents

Description

  The present invention relates to a SAW filter in which a one-terminal-pair surface acoustic wave (hereinafter referred to as SAW) resonator having electrodes formed on a piezoelectric or ferroelectric substrate is connected in a multi-stage ladder shape.

  Conventionally, as a technique related to a SAW filter using a SAW resonator, there is one described in the following literature, for example.

IEICE Transactions A, J76-A [2] (1993-2), Sato et al., “Low Loss Bandpass Filter Using SAW Resonator” P.245-252 IEICE Transactions A, J76-A [2] (1993-2), Hirota et al. “Experiments on SAW filters for mobile radio communications equipment” P.233-244 Journal of Japan Society of Applied Physics, 36 [5B] (1997-5), Noritoshi Kimura et al., “The Power Durability of 900MHz Band Double-Mode-Type Surface Acoustic Wave Filtersand Improvement in Power Durability of Al-Cu Thin Film Electrodes by Cu Atom Segregation “P.3101-3106

  Non-Patent Documents 1 to 3 describe the configuration of the SAW filter, the life of the SAW filter, and the like.

  FIG. 2 is a circuit diagram showing a basic configuration of the conventional SAW filter shown in the documents 1 to 3, and FIG. 3 is a characteristic diagram showing frequency characteristics of FIG.

  In a SAW filter in which a one-terminal-pair SAW resonator is connected in a ladder shape, the SAW resonator 10 is used in a series arm and a parallel arm as shown in FIG. Thus, the high-frequency attenuation pole 13 of the filter is formed, and the low-frequency attenuation pole 14 of the filter is formed by the frequency characteristic 12 of the parallel arm to form a bandpass filter.

  FIG. 4 is a configuration diagram illustrating a main part of the SAW resonator 10 of FIG. 2, in which a perspective view and an enlarged view of a portion A are shown.

  The SAW resonator 10 has an interdigital electrode (hereinafter referred to as IDT) 16 formed on a substrate 15 for transmitting and receiving SAW, and a grating reflector 17 made of a metal strip is disposed on both sides thereof.

  From the theory of the constant K-type filter, the band filter can be realized by matching the resonance frequency of the series arm with the anti-resonance frequency of the parallel arm. Usually, the attenuation amount is insufficient with only one stage, and therefore, for example, a four-stage configuration is used.

  5 is a circuit diagram of a ladder SAW filter having a four-stage configuration, FIG. 6 is a configuration diagram of the SAW filter of FIG. 5, and FIG. 7 is a characteristic diagram showing frequency characteristics of the SAW filter of FIG. is there.

If the ladder-type SAW filter of the four-stage configuration, the SAW resonator 10 _s1 of the series arm of the first stage, the SAW resonator 10 _s2 of the series arm in the second stage, the SAW resonator 10 of the series arm of the third stage _s3 and the fourth-stage SAW resonator _{10s4 in} the series arm form the entire series arm. For this series arm, the SAW resonator 10 _p1 of the parallel arm of the first stage, the SAW resonator 10 _p2 of the parallel arm at the second stage, the SAW resonator 10 _p3 parallel arm of the third stage, 4 The SAW resonator 10 _p4 of the parallel arm at the stage is connected in a ladder shape.

FIG. 8 is a cross-sectional view showing a manufacturing process of a conventional SAW filter.
The SAW filter of FIG. 5 is formed through the steps of FIGS. 8A to 8E, for example.

First, in the process of FIG. 8A, for example, a LiTaO ₃ single crystal substrate 15 having a crystal orientation of 36 ° YX is prepared, and a resist 18 is applied on the pattern formation surface of the substrate 15 by spin coating. In the step of FIG. 8B, an optical mask 19 is set on the substrate 15 coated with the resist 18, and the SAW filter pattern is transferred to the resist 18 by exposing with light 20. In the step of FIG. 8C, the resist 18 unnecessary for development is selectively removed. In the step of FIG. 8D, an electrode metal Al (aluminum) thin film 21 to be the IDT 16 of the SAW resonator is deposited on the entire surface of the substrate 15 from which the unnecessary resist 18 has been removed. 8E, unnecessary portions of the Al thin film 21 are removed together with the resist 18 using an organic solvent.

However, the conventional ladder-type SAW filter has the following problems.
Since the SAW resonators 10 _s1 to 10 _{s4 of the} series arm and the SAW resonators 10 _p1 to 10 _{p4 of the} parallel arm both use standing waves, the energy density is high, and the power resistance is higher than that of the transversal filter. It becomes severe. Further, since SAW is used, the energy of the wave is concentrated in a region within one wavelength from the surface of the substrate 15. That is, the energy density is increased. This becomes particularly severe when there is watt-order input power, such as a recent cellular phone antenna duplexer (duplexer).

  When a large amount of power is input to the SAW device, a strong repeated stress is applied to the IDT 16 that transmits and receives the SAW, so that the Migrel leesn is generated in the electrode metal Al or heat is generated. As a countermeasure, at present, Cu (copper) or Ti (titanium) is added to Al which is an electrode metal to improve stress migration resistance and electromigration resistance in the IDT 16 to improve power resistance. However, in order to improve the power durability in this way, the amount of added metal must be increased, and the added metal is unevenly distributed in Al, or the added metal remains at the time of etching. There was a problem that the value increased.

In order to solve the above problems, a SAW filter according to a first aspect of the present invention includes a substrate having a surface, a first SAW resonator formed on the surface of the substrate, and a surface of the substrate. A bonding pad formed, a connection pattern formed on the surface of the substrate, connecting the first SAW resonator and the bonding pad, and formed on the connection pattern narrower than a width of the connection pattern ; And a dielectric film having a higher thermal conductivity than the substrate.

The SAW filter of the second invention includes a substrate having a surface, a first SAW resonator formed on the surface of the substrate, a second SAW resonator formed on the surface of the substrate, and the substrate of the substrate. A connection pattern formed on the surface for connecting the first SAW resonator and the second SAW resonator, and formed on the connection pattern to be narrower than the width of the connection pattern, and having a higher thermal conductivity than the substrate. And a body membrane.

  As described above in detail, according to the present invention, since the dielectric film is formed on the connection pattern, the heat generated by the vibration of the SAW resonator is transmitted through the dielectric film, thereby improving the heat resistance. Therefore, the power durability is improved.

  In addition, when the connection pattern and the bonding pad are composed of an Al or Al alloy film and a heat dissipation film formed of a metal having a higher thermal conductivity, the heat generated by the vibration of the SAW resonator is generated. It escapes through the heat dissipation film and improves heat resistance. Therefore, the power durability is improved.

  When the connection pattern and bonding pad are made of a metal film pattern with higher thermal conductivity than Al or Al alloy, the heat generated by the vibration of the SAW resonator escapes through the film and improves heat resistance. Let Therefore, the power durability is improved.

  When the connection pattern and the bonding pad are made of an Al or Al alloy film that is 50% or more thicker than the thickness of the electrode of the SAW resonator, the heat generated by the vibration of the SAW resonator is transmitted through the film and escapes. Improve heat resistance. Therefore, the power durability is improved.

  Al or Al alloy film formed by depositing connection patterns and bonding pads on a piezoelectric or ferroelectric single crystal substrate, and a dielectric having higher thermal conductivity than the piezoelectric or ferroelectric single crystal substrate When one or more layers are stacked, the heat generated by the vibration of the SAW resonator is transmitted through the dielectric and escapes, improving the heat resistance. Therefore, the power durability is improved.

  The connection pattern and the bonding pad are composed of a metal film having a higher thermal conductivity than that of Al or Al alloy and one or more layers of a dielectric having a higher thermal conductivity than that of the piezoelectric or ferroelectric single crystal substrate. In this case, the heat generated by the vibration of the SAW resonator is transmitted through the metal film and the dielectric, thereby improving the heat resistance. Therefore, the power durability is improved.

When the dielectric is made of Al ₂ O ₃ , AIN or Si ₃ N ₄ , a heat dissipation effect can be ensured even when a piezoelectric or ferroelectric single crystal substrate is used in a normal SAW resonator or the like.

  When the Al alloy is made by adding Cu, Ti or Ta to Al, the migration resistance can be further improved.

  When the metal having higher thermal conductivity than that of Al or Al alloy is composed of Au, Ag, or Cu, sufficient heat dissipation is obtained.

  As the best mode for carrying out the present invention, preferred embodiments will be described below.

FIG. 9 is a schematic configuration diagram of the ladder-type SAW filter showing the first embodiment of the present invention, and FIG. 10 is a perspective view showing the configuration of the SAW resonator 30 _s1 in FIG.

  The ladder-type SAW filter according to the first embodiment pays attention particularly to heat generation of power durability, and a pattern for connecting between the SAW resonators in the ladder-type SAW filter, a connection pattern for connecting between the SAW resonator and the bonding pad, and For example, by depositing Au (gold) with good thermal conductivity on the bonding pad, the heat generated by the resonator with large heat generation is released to the resonator with low heat generation at the subsequent stage and the external circuit, thereby improving the heat resistance. , Improved withstand power. In particular, since there is a report that the migration of the electrode is accelerated by heat generation, it is important to improve the heat resistance by dispersing and radiating the generated heat.

The ladder-type SAW filter of FIG. 9 is a four-stage SAW filter, similar to the conventional SAW filter of FIG. 5, and includes eight SAW resonators 30 _s1 , 30 _s2 , 30 _s3 , 30 _s4 , 30 _p1 , 30 _p2 , 30 _p3 , 30 _p4 , an input bonding pad 31, an output bonding pad 32, and a plurality of earth bonding pads 33.

The SAW resonator 30 _s1 is the first-stage series arm resonator, the SAW resonator 30 _s2 is the second-stage series arm resonator, and the SAW resonator 30 _s3 is the third-stage series arm resonance. The SAW resonator 30 _s4 is a resonator of the fourth-stage series arm. The SAW resonator 30 _p1 is the resonator of the first-stage parallel arm, the SAW resonator 30 _p2 is the resonator of the second-stage parallel arm, and the SAW resonator 30 _p3 is the resonance of the third-stage parallel arm. The SAW resonator 30 _p4 is a resonator of the fourth-stage parallel arm.

As shown in FIG. 10, the SAW resonator 30 _s1 has an IDT 30a formed of Al or an Al alloy on a substrate 35 and reflectors 30b and 30c formed on both sides of the IDT 30a. The SAW resonators 30 _s2 to 30 _s4 and 30 _p1 to 30 _p4 also have similar IDTs 30a and reflectors 30b and 30c.

Between each SAW resonator 30 _s1 to 30 _s4 , 30 _p1 to 30 _p4 , between the SAW resonator 30 _s1 and the input bonding pad 31, between the SAW resonator 30 _s4 and the output bonding pad 32, and each SAW resonance The four-stage ladder type circuit is configured by connecting the children 30 _p1 to 30 _p4 and the earth bonding pad 33 with the connection pattern 34.

  FIG. 1 is a perspective view of a ladder-type SAW filter pattern showing the first embodiment in FIGS. 9 and 10, and an enlarged partial perspective view of B in FIG. 10 is shown.

  Each of the bonding pads 31 to 33 and the connection pattern 34 includes an Al or Al alloy film 36 formed on the substrate 35, and a heat dissipation film of, for example, Au deposited on the film to improve the heat resistance. 37.

  FIGS. 11A to 11I are cross-sectional views showing manufacturing steps of the SAW filter of FIG.

  The SAW filter shown in FIG. 9 is manufactured by sequentially performing the steps shown in FIGS. The outline of each process will be described below.

First, in the step of FIG. 11A, for example, a LiTaO ₃ single crystal substrate 35 having a crystal orientation of 36 ° YX is prepared, and a resist 38 is applied to the SAW resonator formation planned surface of the substrate 35 by spin coating. . In the step of FIG. 11B, an optical mask 39 is set on the substrate 31 coated with the resist 38 and exposed to light 40, whereby the SAW resonators 30 _s1 to 30 _s4 and 30 _p1 are formed on the resist 38. ˜30 _p4 , bonding pads 31 to 33 and connection pattern 34 are transferred. In the step of FIG. 11C, unnecessary resist 38 is selectively removed by development, and in the step of FIG. 11D, an Al thin film 41 is deposited on the entire upper surface of the substrate 35 from which the unnecessary resist 38 has been removed. To do. In the step of FIG. 11E, unnecessary resist 38 and AL thin film 41 are removed by lift-off using an organic solvent. Through the steps so far, the SAW resonators 30 _s1 to 30 _s4 , 30 _p1 to 30 _p4 , the bonding pads 31 to 33, and the film 36 of the connection pattern 34 are formed on the substrate 35.

In the step of FIG. 11F, a resist 42 is applied again on the surface of the substrate 35 on which the SAW filters 30 _s1 to 30 _s4 , 30 _p1 to 30 _{p4 and the} like are formed. In the step of FIG. 11G, similarly to the steps of FIG. 11B and FIG. 11C, pattern transfer of the film 37 is performed by light exposure using an optical mask, and an unnecessary resist is developed by subsequent development. 42 is removed to expose the surface of the Al thin film 41.

  In the step of FIG. 11H, an Au thin film 43 to be a film 37 is deposited on the entire upper surface of the substrate 35 where the surface of the Al thin film 41 is exposed. In the step of FIG. 11I, an unnecessary thin film 43 is removed together with the resist 42 using an organic solvent. As described above, the film 37 is formed on the bonding pads 31 to 33 and the film 36.

Next, the operation of the SAW filter in FIG. 9 will be described.
When a signal is applied to the input bonding pad 31 via a bonding wire (not shown), electric power passes through the series arm SAW resonators 30 _s1 to 30 _s4 and a larger electric power is applied to the first stage. This is because the power is attenuated by the SAW resonator in the middle as the later stage. That is, it takes the largest power in series-arm SAW resonators 30 _s1, straight Retsuude increased heating value of the SAW resonator 30 _s1 is the best, most become stricter in power durability manner. Therefore, the power resistance of the series arm SAW resonator 30s1 will be described.

Power input to the input bonding pad 31 enters the series arm SAW resonator 30 _s1 of the first stage, the power that passes through the series-arm SAW resonator 30 _s1 includes a series arm of the second-stage SAW resonator 30 _s2 The _signals are input to the first-stage and second-stage parallel arm SAW resonators 30 _p1 and 30 _p2 .

The power input to the series-arm SAW resonators 30 _s1 of the first stage, and vibration is straight Retsuude SAW resonator 30 _s1, SAW constant in a region within one wavelength below the resonator 30 _s1 in the substrate 35 A standing wave is generated, which generates heat.

The heat generated by the series arm SAW resonator 30 _s1 escapes through the heat radiation routes R1 to R5 shown in FIG.

The heat dissipation route R1 is a route that is transmitted from the input side electrode finger of the series arm SAW resonator 30 _s1 to the external circuit through the bonding pad 31 and the bonding wire. The heat dissipation route R2 is a route that is transmitted from the output side electrode finger of the series arm SAW resonator 30 _s1 through the pattern 34 to the series arm SAW resonator 30 _s2 and the parallel arm SAW resonators 30 _p1 and 30 _p2 . The heat dissipation route R3 is a route that travels in the crystal of the substrate 35 from the pattern 34 that extends from the input-side electrode finger of the series arm SAW resonator 30 _s1 to the bonding pad 31. The heat radiation route R4 is a route that travels in the crystal of the substrate 35 from the pattern 34 from the output side electrode finger of the series arm SAW resonator 30 _s1 to the series arm SAW resonator 30 _s2 and the parallel arm SAW resonators 30 _p1 and 30 _p2. It is. The heat radiation route R5 is a route through which heat generated in a region having a depth of one wavelength or less below the series arm SAW resonator 30 _{s1 in} the substrate 35 is transmitted in the lateral direction and the depth direction of the substrate 35.

In the SAW filter of the first embodiment, an Au heat dissipation film 37 is formed on the bonding pads 31 to 33 and the film 36 of the connection pattern 34. Since the thermal conductivities of Al, Au, and LiTaO ₃ are 237, 315, and 4.2 [W / (m · K)], respectively, the heat dissipation effect in the heat dissipation routes R1 to R4 is remarkably improved, resulting in heat resistance. As a result, the withstand power is improved.

For example, in the frequency band of a 900 MHz mobile phone, the film thickness ratio (= film thickness H / frequency λ) of the Al thin film 41 is 11%, the film thickness ratio of the Au thin film 43 is 5%, and the series arm SAW resonator 30 _s1 and A heat dissipation film 37 is formed only on the pattern 34 between the bonding pads 31 and the pattern 34 between the series arm SAW resonator 30 _s1 and the series arm SAW resonator 30 _s2 and the parallel arm SAW resonator 30 _p1. Even if it was evaluated with a simple one formed, a temperature drop of 6% was observed.

  Therefore, the heat generated in the vicinity of the surface of the substrate 35 is quickly dissipated through the film 37 on the surface, not from the inside of the crystal having poor thermal conductivity.

  As described above, in the first embodiment, since the heat dissipation film 37 is formed on the connection pattern 34 and the bonding pads 31 to 33 to improve the heat dissipation, a SAW filter having the following advantages can be obtained. can get.

  (1) There is no need to add a large amount of metal to Al, and the added metal is not unevenly distributed in Al.

  (2) There is no need to add a large amount of metal to Al, and the added metal does not remain during etching.

  (3) It is not necessary to add a large amount of metal to Al, and the resistance value does not increase.

  (4) Since Au is deposited on the film 36, peeling of the film 36 can be prevented.

  (5) Since Au is deposited on the film 36, the electrical resistance of the connection pattern 34 is lowered.

(6) Since the temperature rise at each of the SAW resonators 30 _s2 to 30 _s4 and 30 _p1 to 30 _p4 can be suppressed, the frequency change due to the temperature rise can be suppressed.

  (7) A conventional method for improving migration resistance by adding Cu, Ti, Ta or the like to Al as an electrode metal can be used together, and a synergistic effect can be expected.

  (8) In order to increase the heat dissipation effect, it is not necessary to widen the connection pattern and bonding pads, and it is not necessary to increase the chip size.

  (9) To increase the heat dissipation effect, it is not necessary to widen the connection pattern and bonding pads, and the parasitic capacitance does not increase.

FIG. 12 is a schematic configuration diagram of a ladder-type SAW filter showing Embodiment 2 of the present invention, and FIG. 13 is a perspective view showing a configuration of the SAW resonator 50 _s1 in FIG.

This ladder-type SAW filter is a four-stage SAW filter as in FIG. 9 showing the first embodiment, and includes eight SAW resonators 50 _s1 to 50 _s4 , 50 _p1 to 50 _p4, and an input bonding pad 51. And an output bonding pad 52 and a plurality of ground bonding pads 53.

The SAW resonator 50 _s1 is the resonator of the first-stage series arm, the SAW resonator 50 _s2 is the resonator of the second-stage series arm, and the SAW resonator 50 _s3 is the resonance of the third-stage series arm. The SAW resonator 50 _s4 is a fourth-stage series arm resonator. SAW resonator 50 _p1 is the resonator of the first-stage parallel arm, SAW resonator 50 _p2 is the resonator of the second-stage parallel arm, and SAW resonator 50 _p3 is the resonance of the third-stage parallel arm. The SAW resonator 50 _p4 is a resonator of the fourth-stage parallel arm.

As shown in FIG. 12, the SAW resonator 50 _s1 includes an IDT 50a and reflectors 50b and 50c similar to those in the first embodiment. The SAW resonators 50 _s2 to 50 _s4 and 50 _p1 to 50 _p4 also have similar IDTs 50a and reflectors 50b and 50c.

Between the SAW resonators 50 _s1 to 50 _s4 and 50 _p1 to 50 _p4 , between the SAW resonator 50 _s1 and the input bonding pad 51, between the SAW resonator 50 _s4 and the output bonding pad 52, and each SAW resonance The children 50 _p1 to 50 _p4 and the earth bonding pad 53 are connected by a connection pattern 54 to form a four-stage ladder type circuit.

  FIG. 14 is a perspective view of a ladder-type SAW filter pattern showing the second embodiment shown in FIGS. 12 and 13, and an enlarged partial C perspective view of FIG. 13 is shown.

  In the first embodiment, a heat dissipation film is formed on the connection pattern and the bonding pad. However, in the second embodiment, heat is released between the lower side of the connection pattern 54 and the bonding pads 51 to 53 and the substrate 55. A film 56 is formed. That is, an Al or Al alloy film 57 is laminated on the heat dissipation film pattern 56.

  FIGS. 15A to 15I are cross-sectional views showing manufacturing steps of the SAW filter of FIG.

  The SAW filter of FIG. 12 is manufactured by sequentially performing the steps shown in FIGS. The outline of each process will be described below.

First, in the process of FIG. 15A, for example, a LiTaO ₃ single crystal substrate 55 having a crystal orientation of 36 ° YX is prepared, and a resist 58 is applied to the SAW resonator formation planned surface of the substrate 55 by spin coating. . In the step of FIG. 15B, an optical mask 59 is set on the substrate 55 coated with the resist 58 and exposed with light 60, whereby the pattern of the heat dissipation film 56 of the connection pattern 54 is formed on the resist 58. Transcribed. In the step of FIG. 15C, unnecessary resist 58 is selectively removed by development. In the step of FIG. 15D, an Au thin film 61 is deposited on the entire upper surface of the substrate 55 from which the unnecessary resist 58 has been removed. To do. In the step of FIG. 15E, unnecessary resist 58 and Au thin film 61 are removed by lift-off using an organic solvent. The film 56 is formed on the substrate 55 through the steps so far.

In the step of FIG. 15F, a resist 62 is applied again on the surface of the substrate 55 on which the heat dissipation film 56 is formed. In the step of FIG. 15G, similarly to the steps of FIGS. 15B and 15C, the SAW resonators 50 _s1 to 50 _s4 , 50 _p1 to 50 _p4 , bonding are performed by light exposure using an optical mask. The patterns of the pads 51 to 53 and the film 57 are transferred, and unnecessary resist 62 is removed by subsequent development. The surface of the Au thin film 61 is exposed.

In the step of FIG. _15H , an Al thin film 63 to be the SAW resonators 50 _s1 to 50 _s4 , 50 _p1 to 50 _p4 , and 57 is deposited on the entire upper surface of the substrate 55 where the surface of the Au thin film 61 is exposed. In the step of FIG. 15I, the unnecessary thin film 63 is removed together with the resist 62 using an organic solvent. As described above, the SAW resonators 50 _s1 to 50 _s4 , 50 _p1 to 50 _p4 , the bonding pads 51 to 53 and the connection pattern 54 are formed.

  Next, the operation of this SAW filter will be described with reference to the heat radiation routes R1 to R5 shown in FIG.

In this ladder type SAW filter, power input to the bonding pad 51, enters the series arm SAW resonator 50 _s1 of the first stage, the straight Retsuude SAW resonator 50 _s1 is by vibration, heat is generated . The power passing through the first-stage series arm SAW resonator 50 _s1 is the second-stage series arm SAW resonator 50 _s2 , the first-stage parallel arm SAW resonator 50 _p1, and the second-stage parallel arm SAW resonator. 50 _p2 .

The heat generated in the first-stage series arm SAW resonator 50 _s1 escapes through the same heat radiation routes R1 to R5 as in the first embodiment.

  Here, in the ladder-type SAW filter of the second embodiment, since the heat radiation film 56 is formed in the connection pattern 54 and the bonding pads 51 to 53, the heat radiation routes R1 to R4 are used as in the first embodiment. Heat dissipation is overwhelmingly better than before. Furthermore, since the heat dissipation film 56 is directly deposited on the substrate 55, particularly when the connection pattern 54 is thin and the crystal of the substrate 55 is thick at high frequencies, or when the substrate crystal is fixed to a package with poor heat dissipation. This is very effective when the substrate crystal is connected face down with bumps or the like and heat radiation from the back surface of the substrate crystal cannot be expected.

As described above, in the second embodiment, the heat radiation film 56 is formed below the connection pattern 54 and the bonding pads 51 to 53 to dissipate heat in the SAW resonators 50 _s1 to 50 _s4 and 50 _p1 to 50 _p4 . Thus, a ladder-type SAW filter having the following advantages (11) to (17) can be obtained.

  (11) There is no need to add a large amount of metal to Al, and the added metal is not unevenly distributed in Al.

  (12) There is no need to add a large amount of metal to Al, and the added metal does not remain during etching.

  (13) There is no need to add a large amount of metal to Al, and the resistance value does not increase.

  (14) Since the heat dissipation film 56 for Au is deposited under the Al or AL alloy film 57, peeling of the film 56 can be prevented.

  (15) Since the Au thin film 61 is deposited under the connection pattern 54, the ohmic resistance of the connection pattern 54 decreases.

(16) Since the temperature increase at each of the SAW resonators 50 _s1 to 50 _s4 and 50 _p1 to 50 _p4 can be suppressed, the frequency change due to the temperature increase can be suppressed.

  (17) A conventional method for improving migration resistance by adding Cu, Ti, Ta or the like to Al as an electrode metal can be used in combination, and a synergistic effect can be expected.

FIG. 16 is a schematic configuration diagram of a ladder-type SAW filter showing Embodiment 3 of the present invention, and FIG. 17 is a perspective view showing a configuration of the SAW resonator 70 _s1 in FIG.

This ladder-type SAW filter is a four-stage SAW filter as in FIG. 9 showing the first embodiment, and includes eight SAW resonators 70 _s1 to 70 _s4 , 70 _p1 to 70 _p4, and an input bonding pad 71. And an output bonding pad 72 and a plurality of ground bonding pads 73.

The SAW resonator 70 _s1 is the first-stage series arm resonator, the SAW resonator 70 _s2 is the second-stage series arm resonator, and the SAW resonator 70 _s3 is the third-stage series arm resonance. The SAW resonator 70 _s4 is a fourth-stage series arm resonator. SAW resonator 70 _p1 is the resonator of the first-stage parallel arm, SAW resonator 70 _p2 is the resonator of the second-stage parallel arm, and SAW resonator 70 _p3 is the resonance of the third-stage parallel arm. The SAW resonator 70 _p4 is a resonator of the fourth-stage parallel arm.

As shown in FIG. 17, the SAW resonator 70 _s1 includes an IDT 70a and reflectors 70b and 70c similar to those in the first embodiment. The SAW resonators 70 _s2 to 70 _s4 and 70 _p1 to 70 _p4 also have similar IDTs 70a and reflectors 70b and 70c.

During each SAW resonator _{70 s1 ~70 s4, 70 p1 ~70} p4, between the SAW resonator 70 _s1 and the input bonding pad 71, between the SAW resonator 70 _s4 output bonding pad 72, and the SAW resonator The children 70 _p1 to 70 _p4 and the earth bonding pad 73 are connected by a connection pattern 74 to form a four-stage ladder circuit.

  18 is a perspective view of a ladder-type SAW filter pattern showing the third embodiment shown in FIGS. 16 and 17, and an enlarged view of a portion D of FIG. 17 is shown.

  In the first embodiment, a heat dissipation film is formed above the connection pattern and the bonding pad. However, in this third embodiment, the connection pattern 74 and the bonding pads 71 to 73 are formed only by the heat dissipation film 76. It is formed with.

  FIGS. 19A to 19I are cross-sectional views showing manufacturing steps of the SAW filter of FIG.

  The SAW filter of FIG. 16 is manufactured by sequentially performing the steps shown in FIGS. 19 (a) to 19 (i). The outline of each process will be described below.

First, in the process of FIG. 19A, for example, a LiTaO ₃ single crystal substrate 75 having a crystal orientation of 36 ° YX is prepared, and a resist 77 is applied to the SAW resonator formation planned surface of the substrate 75 by spin coating. . In the step of FIG. 19B, an optical mask 78 is set on the substrate 75 coated with the resist 77 and is exposed with light 79, whereby the resonator pattern is transferred to the resist 77. In the step of FIG. 19C, the unnecessary resist 77 is selectively removed by development, and in the step of FIG. 19D, the Al thin film 80 is deposited on the entire upper surface of the substrate 75 from which the unnecessary resist 78 has been removed. To do. In the step of FIG. 19E, unnecessary resist 77 and Al thin film 80 are removed by lift-off using an organic solvent. Through the steps so far, the SAW resonators 70 _s1 to 70 _s4 and 70 _p1 to 70 _p4 are formed on the substrate 75.

In the step of FIG. 19F, a resist 81 is applied again on the surface of the substrate 75 where the SAW resonators 70 _s1 to 70 _s4 and 70 _p1 to 70 _p4 are formed. In the step of FIG. 19G, the pattern of the connection pattern 74 and the bonding pads 71 to 73 is transferred by light exposure using an optical mask, as in the steps of FIGS. In this development, unnecessary resist 81 is removed, and the surface of the substrate 75 and the ends of the SAW resonators 70 _s1 to 70 _s4 and 70 _p1 to 70 _p4 are exposed.

  In the step shown in FIG. 19H, an Au thin film 82 to be the connection pattern 74 is deposited on the entire upper surface of the substrate 75. In the step of FIG. 19I, the unnecessary thin film 82 is removed together with the resist 81 using an organic solvent. As described above, the connection pattern 74 and the bonding pads 71 to 73 are formed on the substrate 75.

  Next, the operation of this SAW filter will be described with reference to the heat radiation routes R1 to R5 shown in FIG.

In this ladder type SAW filter, power input to the bonding pad 71, enters the series arm SAW resonator 70 _s1 of the first stage, the straight Retsuude SAW resonator 70 _s1 is by vibration, heat is generated . The power passing through the first-stage series arm SAW resonator 70 _s1 is the second-stage series arm SAW resonator 70 _s2 , the first-stage parallel arm SAW resonator 70 _p1, and the second-stage parallel arm SAW resonator. 70 _p2 .

The heat generated in the first-stage series arm SAW resonator 70 _s1 escapes through the same heat radiation routes R1 to R5 as in the first embodiment.

  Here, in the ladder-type SAW filter of the third embodiment, the signal transmission pattern 74 and the bonding pads 71 to 73 are formed of the Au film 82, so that the heat dissipation routes R1 to R1 are the same as in the first embodiment. The heat radiation by R4 is overwhelmingly better than before. Further, since the Au thin film 82 as a heat dissipation route is directly deposited on the substrate 75, the substrate crystal is fixed to a package having poor heat dissipation, especially when the connection pattern 74 is thin and the crystal of the substrate 75 is thick at high frequencies. In this case, it is very effective when the crystal substrate is connected face-down with bumps or the like and heat radiation from the back surface of the crystal substrate cannot be expected.

As described above, in the third embodiment, the connection pattern 74 and the bonding pads 71 to 73 are formed of the Au film to improve the heat dissipation in the SAW resonators 70 _s1 to 70 _s4 and 70 _p1 to 70 _p4 . A ladder-type SAW filter having the advantages (21) to (28) is obtained.

  (21) There is no need to add a large amount of metal to Al, and the added metal is not unevenly distributed in Al.

  (22) There is no need to add a large amount of metal to Al, and the added metal does not remain during etching.

  (23) It is not necessary to add a large amount of metal to Al, and the resistance value does not increase.

  (24) Since the connection pattern 74 is made of Au, the ohmic loss of the device can be reduced.

  (25) Since the connection pattern 74 is deposited / formed only with Au, the film does not peel off due to poor adhesion with other metals, and it is also possible to prevent a decrease in reliability due to diffusion in Al.

(26) Since the temperature rise at each of the SAW resonators 70 _s1 to 70 _s4 and 70 _p1 to 70 _p4 is suppressed, the frequency change due to the temperature increase can be suppressed.

  (27) A conventional method for improving migration resistance by adding Cu, Ti, Ta or the like to Al as an electrode metal can be used together, and a synergistic effect can be expected.

  (28) If the thin electrode fingers and the thick connection pattern 74 are etched or lifted off at the same time, there is a risk that the thin electrode fingers are excessively etched or lifted off. However, in the third embodiment, the electrode fingers and the connection pattern 74 are different from each other. Since it is formed in a process, control is easy.

20 is a schematic configuration diagram of a ladder-type SAW filter showing a fourth embodiment of the present invention, and FIG. 21 is a perspective view showing a configuration of the SAW resonator 90 _s1 in FIG.

This ladder-type SAW filter is a SAW filter having a four-stage configuration, similar to FIG. 9 showing the first embodiment, and includes eight SAW resonators 90 _{s1 to} 90 _s4 , 90 _{p1 to} 90 _p4, and an input bonding pad 91. And an output bonding pad 92 and a plurality of ground bonding pads 93.

The SAW resonator 90 _s1 is the first-stage series arm resonator, the SAW resonator 90 _s2 is the second-stage series arm resonator, and the SAW resonator 90 _s3 is the third-stage series arm resonance. The SAW resonator 90 _s4 is a fourth-stage series arm resonator. SAW resonator 90 _p1 is the resonator of the first-stage parallel arm, SAW resonator 90 _p2 is the resonator of the second-stage parallel arm, and SAW resonator 90 _p3 is the resonance of the third-stage parallel arm. The SAW resonator 90 _p4 is a resonator of the fourth-stage parallel arm.

As shown in FIG. 21, the SAW resonator 90 _s1 includes an IDT 90a and reflectors 90b and 90c similar to those in the first embodiment. The SAW resonators 90 _{s2 to} 90 _s4 and 90 _{p1 to} 90 _p4 also have similar IDTs 90a and reflectors 90b and 90c.

Between each SAW resonator 90 _{s1 to} 90 _s4 and 90 _{p1 to} 90 _p4 , between the SAW resonator 90 _s1 and the input bonding pad 91, between the SAW resonator 90 _s4 and the output bonding pad 92, and each SAW resonance The children 90 _{p1 to} 90 _p4 and the ground bonding pad 93 are connected by a connection pattern 94 to form a four-stage ladder type circuit.

  FIG. 22 is a perspective view of a ladder-type SAW filter pattern showing the fourth embodiment shown in FIGS. 20 and 21, and an E partial enlarged view of FIG. 21 is shown.

In the first embodiment, a heat dissipation film is formed on the upper side of the connection pattern and the bonding pad. However, in the fourth embodiment, the connection pattern 94 and the bonding pads 91 to 93 are connected to the resonators 90 _{s1 to} 90 _s4. , 90 _{p1 to} 90 _{p4, the} Al or Al alloy film 96 is thicker than 50%.

  FIGS. 23A to 23I are cross-sectional views showing manufacturing steps of the SAW filter of FIG.

  The SAW filter of FIG. 20 is manufactured by sequentially performing the steps shown in FIGS. The outline of each process will be described below.

First, in the process of FIG. 23A, for example, a LiTaO ₃ single crystal substrate 95 having a crystal orientation of 36 ° YX is prepared, and a resist 97 is applied to the SAW resonator formation planned surface of the substrate 95 by spin coating. . In the step of FIG. 23B, an optical mask 98 is set on the substrate 95 on which the resist 97 is applied, and the pattern of the resonator is transferred to the resist 97 by exposing with light 99. In the step of FIG. 23C, the unnecessary resist 97 is selectively removed by development, and in the step of FIG. 23D, the Al thin film 100 is deposited on the entire upper surface of the substrate 95 from which the unnecessary resist 98 is removed. To do. In the step of FIG. 23E, unnecessary resist 97 and Al thin film 100 are removed by lift-off using an organic solvent. Through the steps so far, the SAW resonators 90 _{s1 to} 90 _s4 and 90 _{p1 to} 90 _p4 are formed on the substrate 95.

In the step of FIG. _23F , the resist 101 is applied again on the surface of the substrate 95 on which the SAW resonators 90 _{s1 to} 90 _s4 and 90 _{p1 to} 90 _p4 are formed. In the step of FIG. 23 (g), similarly to the steps of FIGS. 23 (b) and (c), the pattern of the connection pattern 94 and the bonding pads 91 to 93 is transferred by light exposure using an optical mask, and thereafter In this development, the unnecessary resist 101 is removed, and the surface of the substrate 95 and the ends of the SAW resonators 90 _{s1 to} 90 _s4 and 90 _{p1 to} 90 _p4 are exposed.

  In the step shown in FIG. 23H, an Au thin film 102 to be a connection pattern 94 is deposited on the entire upper surface of the substrate 95. In the step of FIG. 23I, an unnecessary thin film 102 is removed together with the resist 101 using an organic solvent. As described above, the connection pattern 94 and the bonding pads 91 to 93 are formed on the substrate 95.

  Next, the operation of this SAW filter will be described with reference to the heat radiation routes R1 to R5 shown in FIG.

In this ladder type SAW filter, the power input to the bonding pad 91, enters the series arm SAW resonator 90 _s1 of the first stage, the straight Retsuude SAW resonator 90 _s1 is by vibration, heat is generated . The power passing through the first-stage series arm SAW resonator 90 _s1 is the second-stage series arm SAW resonator 90 _s2 , the first-stage parallel arm SAW resonator 90 _p1, and the second-stage parallel arm SAW resonator. 90 _p2 .

The heat generated by the first-stage serial arm SAW resonator 90 _s1 escapes through the same heat radiation routes R1 to R5 as in the first embodiment.

  Here, in the ladder-type SAW filter of the fourth embodiment, since the connection pattern 94 and the bonding pads 91 to 93 are formed of a thick film of Al or Al alloy, similarly to the first embodiment, the heat dissipation route. The heat dissipation by R1 to R4 is overwhelmingly better than before. In addition, since Al or Al alloy serving as a heat dissipation route is directly deposited on the substrate 95, particularly when the connection pattern 94 is thin and the crystal of the substrate 95 is thick at high frequencies, or the substrate crystal is a package with poor heat dissipation. When fixed, the substrate crystal is connected face down with bumps or the like, and this is very effective when heat radiation from the back surface of the substrate crystal cannot be expected.

As described above, in the fourth embodiment, the connection pattern 94 and the bonding pads 91 to 93 are formed of thick Al or Al alloy to improve heat dissipation in the SAW resonators 90 _{s1 to} 90 _s4 and 90 _{p1 to} 90 _p4 . Therefore, a ladder-type SAW filter having the following advantages (31) to (37) can be obtained.

  (31) It is not necessary to add a large amount of metal to Al, and the added metal is not unevenly distributed in Al.

  (32) There is no need to add a large amount of metal to Al, and the added metal does not remain during etching.

  (33) There is no need to add a large amount of metal to Al, and the resistance value does not increase.

  (34) Since the connection pattern 94 is made of Al, it is not necessary to add a special process.

  (35) Since the connection pattern 94 is formed by vapor deposition of only Al, the film does not peel off due to poor adhesion with other metals, and the reliability deterioration due to diffusion of other metals in Al can be prevented.

(36) Since the temperature increase at each of the SAW resonators 90 _{s2 to} 90 _s4 and 90 _{p1 to} 90 _p4 can be suppressed, the frequency change due to the temperature increase can be suppressed.

  (37) A conventional method for improving migration resistance by adding Cu, Ti, Ta or the like to Al of the electrode metal can be used together, and a synergistic effect can be expected.

FIG. 24 is a schematic configuration diagram of a ladder-type SAW filter showing the fifth embodiment of the present invention, and FIG. 25 is a perspective view showing a configuration of the SAW resonator 110 _s1 in FIG.

This ladder-type SAW filter is a four-stage SAW filter as in FIG. 9 showing the first embodiment, and includes eight SAW resonators 110 _{s1 to} 110 _s4 , 110 _{p1 to} 110 _p4, and an input bonding pad 111. And an output bonding pad 112 and a plurality of ground bonding pads 113.

The SAW resonator 110 _s1 is the first-stage series arm resonator, the SAW resonator 110 _s2 is the second-stage series arm resonator, and the SAW resonator 110 _s3 is the third-stage series arm resonance. The SAW resonator 110 _s4 is a fourth-stage series arm resonator. SAW resonator 110 _p1 is the resonator of the first-stage parallel arm, SAW resonator 110 _p2 is the resonator of the second-stage parallel arm, and SAW resonator 110 _p3 is the resonance of the third-stage parallel arm. The SAW resonator 110 _p4 is a resonator of the fourth-stage parallel arm.

As shown in FIG. 25, the SAW resonator 110 _s1 includes an IDT 110a and reflectors 110b and 110c similar to those in the first embodiment. The SAW resonators 110 _{s2 to} 110 _s4 and 110 _{p1 to} 110 _p4 also have similar IDTs 110a and reflectors 110b and 110c.

During each SAW resonator _{110 s1 ~110 s4, 110 p1 ~110} p4, between the SAW resonator 110 _s1 and the input bonding pad 111, between the SAW resonator 110 _s4 output bonding pad 112, and the SAW resonator The children 110 _{p1 to} 110 _p4 and the earth bonding pad 113 are connected by the connection pattern 114 to form a four-stage ladder type circuit.

  FIG. 26 is a perspective view of a ladder-type SAW filter pattern showing Example 5 in FIGS. 24 and 25, and an F partial enlarged perspective view of FIG. 25 is shown.

  In the first embodiment, a heat dissipation film is formed above the connection pattern and the bonding pad. However, in this fifth embodiment, the thermal conductivity is higher than that of the substrate 115 above the connection pattern 114 and the bonding pads 111 to 113. A large dielectric film 116 is deposited to improve heat resistance.

  FIGS. 27A to 27I are cross-sectional views showing manufacturing steps of the SAW filter of FIG.

  The SAW filter of FIG. 24 is manufactured by sequentially performing the steps shown in FIGS. The outline of each process will be described below.

First, in the process of FIG. 27A, for example, a LiTaO ₃ single crystal substrate 115 having a crystal orientation of 36 ° YX is prepared, and a resist 117 is applied to the surface of the substrate 115 where a SAW resonator is to be formed by spin coating. . In the step of FIG. 27B, the optical mask 118 is set on the substrate 115 coated with the resist 117 and exposed to light 119, whereby the SAW resonators 110 _{s1 to} 110 _s4 and 110 _p1 are formed on the resist 117. 110 _p4 , bonding pads 111 to 113, and connection pattern 114 are transferred. In the step of FIG. 27C, unnecessary resist 117 is selectively removed by development, and in the step of FIG. 27D, an Al thin film 120 is deposited on the entire upper surface of the substrate 115 from which the unnecessary resist 118 has been removed. To do. In the step of FIG. 27E, unnecessary resist 117 and Al thin film 120 are removed by lift-off using an organic solvent. Through the steps so far, the SAW resonators 110 _{s1 to} 110 _s4 and 110 _{p1 to} 110 _p4 , the bonding pads 111 to 113 and the base of the connection pattern 114 are formed on the substrate 115.

In the step of FIG. 27F, a resist 121 is applied again on the surface of the substrate 115 on which the SAW resonators 110 _{s1 to} 110 _s4 and 110 _{p1 to} 110 _p4 are formed. In the step of FIG. 27G, the pattern of the connection pattern 114 and the bonding pads 111 to 113 is transferred by light exposure using an optical mask, as in the steps of FIGS. With this development, unnecessary resist 121 is removed, and the underlying pattern of the connection pattern 114 and the bonding pads 111 to 113 is exposed.

In the step of FIG. 27 (h), a dielectric film 122 having a high conductivity, such as an Al ₂ O ₃ film, is deposited on the entire surface of the substrate 115 from above. The thermal conductivity of Al ₂ O ₃ is 21 [W / (m · K)]. In the step of FIG. 27I, the unnecessary film 122 is removed together with the resist 121 using an organic solvent. Thus, the connection pattern 114 and the bonding pads 111 to 113 with the film 116 on the upper side are formed on the substrate 115.

  Next, the operation of this SAW filter will be described with reference to the heat radiation routes R1 to R5 shown in FIG.

In this ladder type SAW filter, the power input to the bonding pad 91, enters the series arm SAW resonator 110 _s1 of the first stage, the straight Retsuude SAW resonator 110 _s1 is by vibration, heat is generated . The power passing through the first-stage series arm SAW resonator 110 _s1 is the second-stage series arm SAW resonator 110 _s2 , the first-stage parallel arm SAW resonator 110 _p1, and the second-stage parallel arm SAW resonator. 110 _p2 .

The heat generated in the first-stage serial arm SAW resonator 110 _s1 escapes through the heat dissipation routes R1 to R5 similar to those in the first embodiment.

  Here, in the ladder-type SAW filter of the fifth embodiment, since the film 116 having high thermal conductivity is formed on the connection pattern 114 and the bonding pads 111 to 113, the same as in the first embodiment. In addition, the heat radiation by the heat radiation routes R1 to R4 is overwhelmingly better than the conventional one. Further, particularly when the connection pattern 114 is thin and the substrate 115 is thick at high frequencies, or when the substrate crystal is fixed to a package with poor heat dissipation, the substrate crystal is connected face down with bumps or the like. This is very effective when heat dissipation from the back surface of the glass cannot be expected.

As described above, in the fifth embodiment, the connection pattern 114 and the bonding pads 111 to 113 are formed of the Al or Al alloy film and the dielectric film 116 having a high thermal conductivity, and each SAW resonator 110 is formed. _Since heat dissipation in _{s1 to} 110 _s4 and 110 _{p1 to} 110 _p4 is improved, a ladder-type SAW filter having the following advantages (41) to (47) can be obtained.

  (41) There is no need to add a large amount of metal to Al, and the added metal is not unevenly distributed in Al.

  (42) There is no need to add a large amount of metal to Al, and the added metal does not remain during etching.

  (43) There is no need to add a large amount of metal to Al, and the resistance value does not increase.

  (44) Since the upper side of the connection pattern 114 is the dielectric film 116, the pattern can be protected.

  (45) The dielectric film 116 can be deposited on portions other than the connection pattern 114 and the bonding pads 111 to 113 that do not affect the electrical characteristics. Can improve heat dissipation.

(46) Since the temperature increase at each of the SAW resonators 110 _{s1 to} 110 _s4 and 110 _{p1 to} 110 _p4 is suppressed, the frequency change due to the temperature increase can be suppressed.

  (47) A conventional method for improving migration resistance by adding Cu, Ti, Ta or the like to Al as an electrode metal can be used in combination, and a synergistic effect can be expected.

FIG. 28 is a schematic configuration diagram of a ladder-type SAW filter showing Embodiment 6 of the present invention, and FIG. 29 is a perspective view showing a configuration of the SAW resonator 130 _s1 in FIG.

This ladder-type SAW filter is a four-stage SAW filter as in FIG. 9 showing the first embodiment, and includes eight SAW resonators 130 _{s1 to} 130 _s4 , 130 _{p1 to} 130 _p4, and an input bonding pad 131. And an output bonding pad 132 and a plurality of ground bonding pads 133.

The SAW resonator 130 _s1 is a first-stage series arm resonator, the SAW resonator 130 _s2 is a second-stage series arm resonator, and the SAW resonator 130 _s3 is a third-stage series arm resonance. The SAW resonator 130 _s4 is a fourth-stage series arm resonator. SAW resonator 130 _p1 is the resonator of the first-stage parallel arm, SAW resonator 130 _p2 is the resonator of the second-stage parallel arm, and SAW resonator 130 _p3 is the resonance of the third-stage parallel arm. The SAW resonator 130 _p4 is the resonator of the fourth-stage parallel arm.

As shown in FIG. 29, the SAW resonator 130 _s1 includes the same IDT 130a and reflectors 130b and 130c as in the first embodiment. The SAW resonators 130 _{s2 to} 130 _s4 and 130 _{p1 to} 130 _p4 also have similar IDTs 130a and reflectors 130b and 130c.

Between each SAW resonator 130 _{s1 to} 130 _s4 and 130 _{p1 to} 130 _p4 , between the SAW resonator 130 _s1 and the input bonding pad 131, between the SAW resonator 130 _s4 and the output bonding pad 132, and each SAW resonance The children 130 _{p1 to} 130 _p4 and the earth bonding pad 133 are connected by a connection pattern 134 to form a four-stage ladder type circuit.

  FIG. 30 is a perspective view of a ladder-type SAW filter pattern showing Example 6 in FIGS. 28 and 29, and an enlarged G perspective view of FIG. 29 is shown.

  In the first embodiment, a heat dissipation film is formed on the upper side of the connection pattern and the bonding pad. However, in the sixth embodiment, the connection pattern 134 and the bonding pads 131 to 133 are formed on the substrate, and the Al or Al alloy film 136 is formed on the substrate. A heat radiation film 137 is laminated thereon, and a dielectric film 138 having a high thermal conductivity is further laminated thereon to improve heat resistance.

  FIGS. 31A to 31M are cross-sectional views showing manufacturing steps of the SAW filter of FIG.

  The SAW filter of FIG. 28 is manufactured by sequentially performing the steps shown in FIGS. The outline of each process will be described below.

First, in the process of FIG. 31A, for example, a LiTaO ₃ single crystal substrate 135 having a crystal orientation of 36 ° YX is prepared, and a resist 139 is applied to the SAW resonator formation planned surface of the substrate 135 by spin coating. . In the step of FIG. 31B, the optical mask 140 is set on the substrate 135 coated with the resist 139 and exposed to light 141, whereby the SAW resonators 130 _{s1 to} 130 _s4 and 130 _p1 are formed on the resist 139. To 130 _p4 , bonding pads 131 to 133, and the pattern of the film 136 of the connection pattern 134 are transferred. In the step of FIG. 31C, unnecessary resist 139 is selectively removed by development, and in the step of FIG. 31D, an Al thin film 142 is deposited on the entire upper surface of the substrate 135 from which the unnecessary resist 139 has been removed. To do. In the step of FIG. 31E, unnecessary resist 139 and Al thin film 142 are removed by lift-off using an organic solvent. The SAW resonators 130 _{s1 to} 130 _s4 and 130 _{p1 to} 130 _p4 , the bonding pads 131 to 133, and the underlying film 136 of the connection pattern 134 are formed on the substrate 135 through the steps so far.

In the step of FIG. 31F, a resist 143 is applied again on the surface of the substrate 135 on which the SAW resonators 130 _{s1 to} 130 _s4 130 _{p1 to} 130 _{p4 and the} like are formed. In the step of FIG. 31G, the pattern of the connection pattern 134 and the film 136 of the bonding pads 131 to 133 is transferred by light exposure using an optical mask, as in the steps of FIGS. Then, in the subsequent development, unnecessary resist 143 is removed, and the pattern of the film 136 of the connection pattern 134 and the bonding pads 131 to 133 is exposed.

  In the step of FIG. 31H, an Au thin film 144 to be a film 137 is deposited on the entire surface from the upper side of the substrate 135. In the step of FIG. 31I, an unnecessary film 144 is removed together with the resist 143 using an organic solvent.

  In the step of FIG. 31J, a resist 145 is applied again from the upper side of the substrate 135 to the entire surface. In the step of FIG. 31 (k), similarly to the steps of FIGS. 31 (b) and (c), the pattern of the film 138 of the connection pattern 134 and the bonding pads 131 to 133 is transferred by light exposure using an optical mask. Then, unnecessary resist 145 is removed by subsequent development, and the connection pattern 134 and the pattern of the film 137 of the bonding pads 131 to 133 are exposed.

In the step of FIG. 31 (l), a dielectric Al ₂ O ₃ film 146 having a high conductivity and serving as the film 138 is deposited on the entire surface of the substrate 135 from above. In the step of FIG. 31M, an unnecessary film 146 is removed together with the resist 145 using an organic solvent. As described above, the three-layer connection pattern 134 and the bonding pads 131 to 133 are formed on the substrate 135.

  Next, the operation of this SAW filter will be described with reference to the heat radiation routes R1 to R5 shown in FIG.

In this ladder type SAW filter, power input to the bonding pad 131 enters the series arm SAW resonator 130 _s1 of the first stage, the straight Retsuude SAW resonator 130 _s1 is by vibration, heat is generated . The power passing through the first-stage series arm SAW resonator 130 _s1 is the second-stage series arm SAW resonator 130 _s2 , the first-stage parallel arm SAW resonator 130 _p1, and the second-stage parallel arm SAW resonator. 130 _p2 .

The heat generated in the first-stage series arm SAW resonator 130 _s1 escapes through the heat dissipation routes R1 to R5 similar to those in the first embodiment.

  Here, in the ladder-type SAW filter of the sixth embodiment, the connection pattern 134 and the bonding pads 131 to 133 are made of an Al or Al alloy film 136, an Au heat dissipation film 137, and a high thermal conductivity. Since it is composed of the dielectric film 138, the heat radiation by the heat radiation routes R1 to R4 is overwhelmingly improved as in the first embodiment. Furthermore, particularly when the connection pattern 134 is thin and the substrate 135 is thick, or when the substrate crystal is fixed to a package with poor heat dissipation, the substrate crystal is connected face-down with bumps or the like. This is very effective when heat dissipation from the back surface of the glass cannot be expected.

  As described above, in the sixth embodiment, the connection pattern 134 and the bonding pads 131 to 133 are formed of the Al or Al alloy film 136, the Au heat dissipation film 137, and the dielectric film 138 having a high thermal conductivity. Therefore, the ladder-type SAW filter having the following advantages (51) to (60) can be obtained.

  (51) There is no need to add a large amount of metal to Al, and the added metal is not unevenly distributed in Al.

  (52) There is no need to add a large amount of metal to Al, and the added metal does not remain during etching.

  (53) There is no need to add a large amount of metal to Al, and the resistance value does not increase.

  (54) Since the Au film 137 is deposited on the Al film 136, peeling of the film 136 can be prevented.

  (55) Since the Au film 137 is deposited on the Al film 136, the cross-sectional area of the connection pattern 134 is increased, and the resistance can be reduced.

(56) Since the temperature rise at each of the SAW resonators 130 _{s1 to} 130 _s4 and 130 _p1 to 10 _p4 is suppressed, the frequency change due to the temperature rise can be suppressed.

  (57) A conventional method for improving migration resistance by adding Cu, Ti, Ta or the like to Al as an electrode metal can be used together, and a synergistic effect can be expected.

  (58) Since the upper side of the connection pattern 134 is the dielectric film 138, the pattern can be protected. Since it is made of Al, it is not necessary to add a special process.

  (59) Since the uppermost portion of the connection pattern 134 is the dielectric film 138, peeling of the Au film 137 can be prevented.

  (60) The dielectric film 138 can be deposited on the portions other than the connection pattern 134 and the bonding pads 131 to 133 that do not affect the electrical characteristics. Can improve heat dissipation.

  In addition, this invention is not limited to the said Example, A various deformation | transformation is possible. Examples of such modifications include the following.

  (I) In Examples 1 to 3 and Example 5, Au was used as a metal having higher thermal conductivity than Al or AL alloy. However, Ag and Cu also have high thermal conductivity, and 426 [W / ( m · K)], 398 [W / (m · K)], the same effect can be obtained by using these.

  (Ii) In Examples 1, 2 and 5, the metal films 37 and 56 having higher thermal conductivity than that of Al or AL alloy are formed in one layer.

(Iii) In Examples 5 and 6, the dielectric having higher thermal conductivity than the substrate is Al ₂ O ₃ , but AIN and Si ₃ N ₄ can also be used. The thermal conductivity of AIN or Si ₃ N ₄ is 200 [W / (m · K)], 5.5 [W / (m · K)]. Also, Ag and Cu have high thermal conductivity and are 426 [W / (m · K)] and 398 [W / (m · K)], respectively.

  (Iv) In the fifth and sixth embodiments, the dielectric films 116 and 138 having a higher thermal conductivity than the substrate are formed as one layer, but may be formed in multiple layers.

(V) A dielectric Al ₂ O ₃ having a higher thermal conductivity than the substrate may be laminated on the film 76 of the third embodiment or the film 96 of the fourth embodiment.

(Vi) In the manufacturing process described in Examples 1 to 6, lift-off is applied to Al or Al ₂ O ₃ , but etching may be performed.

It is a perspective view of the pattern of the ladder type SAW filter which shows Example 1 of this invention. It is a circuit diagram which shows the basic composition of the conventional SAW filter. It is a characteristic view which shows the frequency characteristic of FIG. FIG. 3 is a configuration diagram illustrating a main part of the SAW resonator 10 of FIG. 2. It is a circuit diagram of a ladder type SAW filter having a four-stage configuration. It is a block diagram of the SAW filter of FIG. FIG. 6 is a characteristic diagram showing frequency characteristics of the SAW filter of FIG. 5. It is sectional drawing which shows the manufacturing process of the conventional SAW filter. 1 is a schematic configuration diagram of a ladder-type SAW filter showing Embodiment 1 of the present invention. FIG. 10 is a perspective view showing a configuration of a SAW resonator 30 _s1 in FIG. 9. It is sectional drawing which shows the manufacturing process of the SAW filter of FIG. It is a schematic block diagram of the ladder type SAW filter which shows Example 2 of this invention. It is a perspective view which shows the structure of SAW resonator 50 _s1 in FIG. It is a perspective view of the pattern of the ladder type SAW filter which shows Example 2 of this invention. It is sectional drawing which shows the manufacturing process of the SAW filter of FIG. It is a schematic block diagram of the ladder type SAW filter which shows Example 3 of this invention. It is a perspective view which shows the structure of SAW resonator 70 _s1 in FIG. It is a perspective view of the pattern of the ladder type SAW filter which shows Example 3 of this invention. FIG. 17 is a cross-sectional view showing a manufacturing process of the SAW filter of FIG. 16. It is a schematic block diagram of the ladder type SAW filter which shows Example 4 of this invention. FIG. ₂₁ is a perspective view illustrating a configuration of a SAW resonator 90 _s1 in FIG. 20. It is a perspective view of the pattern of the ladder type SAW filter which shows Example 4 of this invention. FIG. 21 is a cross-sectional view showing a manufacturing process of the SAW filter of FIG. 20. It is a schematic block diagram of the ladder type SAW filter which shows Example 5 of this invention. FIG. ₂₅ is a perspective view showing a configuration of a SAW resonator 110 _s1 in FIG. 24. It is a perspective view of the pattern of the ladder type SAW filter which shows Example 5 of this invention. FIG. 25 is a cross-sectional view showing a manufacturing process of the SAW filter of FIG. 24. It is a schematic block diagram of the ladder type SAW filter which shows Example 6 of this invention. It is a perspective view which shows the structure of SAW resonator 130 _s1 in FIG. It is a perspective view of the pattern of the ladder type SAW filter which shows Example 6 of this invention. It is sectional drawing which shows the manufacturing process of the SAW filter of FIG.

Explanation of symbols

10 _s1 to 10 _s4 , 10 _p1 to 10 _p4 , 30 _s1 to 30 _s4 , 30 _p1 to 30 _p4 , 50 _s1 to 50 _s4 , 50 _p1 to 50 _p4 , 70 _s1 to 70 _s4 , 70 _p1 to 70 _p4 , 90 _s1 ˜90 _s4 , 90 _p1 ˜90 _p4 , 110 _s1 ˜110 _s4 , 110 _p1 ˜110 _p4 , 130 _s1 ˜130 _s4 , 130 _p1 ˜130 _p4 SAW resonators 11 ˜13, 31 ˜33, 51 ˜53, 71 ˜ 73, 91-93, 111-113, 131-133 Bonding pads 14, 34, 54, 74, 94, 114, 134 Connection patterns 15, 35, 55, 75, 95, 115, 135 Substrate 10a, 30a, 50a, 70a, 90a, 110a, 130a IDT
36, 57, 94, 134 Al or Al alloy film 37, 56, 74, 137 Au film 116, 138 Dielectric film

Claims (2)

A substrate with a surface;
A first surface acoustic wave resonator formed on the surface of the substrate;
A bonding pad formed on the surface of the substrate;
A connection pattern formed on the surface of the substrate and connecting the first surface acoustic wave resonator and the bonding pad;
A dielectric film formed on the connection pattern narrower than the width of the connection pattern, and having a higher thermal conductivity than the substrate;
A surface acoustic wave filter comprising: A substrate with a surface;
A first surface acoustic wave resonator formed on the surface of the substrate;
A second surface acoustic wave resonator formed on the surface of the substrate;
A connection pattern formed on the surface of the substrate and connecting the first surface acoustic wave resonator and the second surface acoustic wave resonator;
A dielectric film formed on the connection pattern narrower than the width of the connection pattern, and having a higher thermal conductivity than the substrate;
A surface acoustic wave filter comprising:

Images