JP4066952B2 - Electronic component element, electronic component, and communication device - Google Patents

Description

  The present invention relates to an electronic component element such as a surface acoustic wave device that can be reduced in size and has excellent yield and stability over time, an electronic component using the device in a package, and a communication device including the electronic component element It is.

  Conventionally, in a small communication device such as a cellular phone, a band pass filter having a pass band frequency within a range of several tens of MHz to several GHz is often used as an electronic component. As an example of the band-pass filter, a surface acoustic wave (hereinafter referred to as SAW) device that can be miniaturized can be cited. The SAW device is a device in which a SAW element having a plurality of comb-shaped electrode portions combined on a piezoelectric substrate so as to exhibit a filter function is housed in a package.

  The comb electrode section is an electric signal-surface wave transducer (Inter Digital Transducer, hereinafter referred to as IDT) having interdigital electrodes that are interleaved with each other. Examples of combinations of the IDTs include types such as a longitudinally coupled resonator type, a laterally coupled resonator type, a transversal type, a ladder type, and a lattice type.

  In order to meet the demand for miniaturization of SAW devices due to the miniaturization of mobile phones, the connection of SAW elements formed in a chip shape to a package is not a wire bonding connection as in the prior art, but a bump connection using Au bumps. It has been adopted.

  The Au bump is formed by crimping a ball formed at the tip of the Au wire to the electrode pad formed on the piezoelectric substrate surface of the chip-like SAW element by applying ultrasonic waves, and then the base end portion of the ball The Au wire is cut from the wire.

  Patent document 1 is mentioned as a prior art regarding the layer structure of the electrode pad in which Au bump is formed. In Patent Document 1, as the electrode pad layer structure, a lower electrode formed of Al, an intermediate electrode (consisting of a NiCr layer, an Al layer, and a Ti layer) and Al are formed from the element substrate side. And an upper layer electrode are disclosed.

The reason why this electrode pad is formed in the above layer configuration is that there is a problem that cracks and cracks occur in the piezoelectric substrate of the SAW device due to thermal shock or drop impact, and the material of the lower electrode, upper electrode and intermediate electrode in the above layer configuration Further, by making the thickness of the intermediate electrode an appropriate value, the occurrence of the cracks and cracks can be prevented. Here, since it is necessary to form the lower electrode simultaneously with the IDT, the thickness of the lower electrode cannot be freely changed.
JP 2001-313305 A (publication date: November 9, 2001)

  However, when a thermal shock or a drop impact is applied to the SAW device as described above, there is a case where a joint failure may occur at a joint portion between an Al electrode pad layer and an Au bump in an electronic component such as a SAW device. A problem has occurred.

  An object of the present invention is to provide an electronic component element such as a SAW element, an electronic component, and a communication device that can use bump bonding that can be miniaturized and can improve the yield and stability of characteristics over time.

  The present inventors diligently studied the above-mentioned problems. As a result, the occurrence of joint failure is caused by a small joint diffusion diameter (a diameter of a circular portion where the AuAl-based alloy is formed under the Au bump) and a small joint area. The inventors have found that this is sufficient, and have completed the present invention.

  In order to solve the above problems, an electronic component element according to the present invention is formed on a substrate, an electronic function unit formed on the substrate, an electrode pad connected to the electronic function unit, and the electrode pad. The uppermost layer in contact with the Au bump in the electrode pad is made of a triaxially oriented Al film.

  According to the above configuration, since the uppermost layer in contact with the Au bump is a triaxially oriented Al film, the layer hardness of the uppermost layer can be reduced, and at the joint portion between the Au bump and the uppermost layer made of the triaxially oriented Al film. The diffusion diameter of the bonding (the diameter of the circular portion where the AuAl-based alloy is formed under the Au bump) can be made larger than in the past.

  As a result, the above structure can improve the bonding strength by increasing the bonding area, improve the thermal shock resistance and the drop impact resistance, and improve the yield during manufacturing and the stability of characteristics over time. Is possible.

  In the electronic component element, it is preferable that a diffusion barrier layer is provided in the lowermost layer of the electrode pad. In the electronic component element, the electrode pad preferably further includes a lower electrode layer, an adhesive layer, and a stress relaxation layer from the substrate side between the substrate and the diffusion barrier layer.

  In the electronic component element, the diffusion barrier layer may be made of Ti. In the electronic component element, it is preferable that the diffusion barrier layer has a thickness of 60 nm or more. According to the above configuration, the formation of the triaxially oriented Al film on the diffusion barrier layer can be ensured by setting the thickness of the diffusion barrier layer to 60 nm or more.

  In the electronic component element, the substrate may be a piezoelectric substrate, and the electronic function unit may be a comb-shaped electrode unit formed on the piezoelectric substrate.

  In order to solve the above-described problems, an electronic component according to the present invention includes any one of the electronic component elements described above and a package in which an external electrode is formed at a position corresponding to the Au bump. It is a feature.

  According to the above configuration, by providing the Au bump that connects the electrode pad and the external electrode to each other, the external electrode can be formed within the area facing the surface of the substrate. As compared with the conventional electronic parts by wire bonding that need to be provided outside, the size can be reduced.

  In addition, since the above configuration includes the electronic component element according to the present invention, as described above, the bonding strength can be improved by increasing the bonding area, and the thermal shock resistance and the drop impact resistance can be improved. Thus, it is possible to improve the yield during manufacturing and the stability of characteristics over time.

  In order to solve the above-mentioned problem, a communication device according to the present invention includes any one of the electronic component elements described above or the electronic component.

  According to the above configuration, by providing the electronic component element according to any of the above, or the electronic component, it is possible to reduce the size and improve the thermal shock resistance and the drop impact resistance, It becomes possible to improve the yield at the time of manufacture and the stability of characteristics over time.

  As described above, the electronic component element according to the present invention includes a substrate, an electronic function unit formed on the substrate, an electrode pad connected to the electronic function unit, and an Au bump formed on the electrode pad. The uppermost layer in contact with the Au bump in the electrode pad is composed of a triaxially oriented Al film.

  Therefore, in the above configuration, since the uppermost layer in contact with the Au bump is a triaxially oriented Al film, the layer hardness of the uppermost layer can be reduced, and the junction between the Au bump and the uppermost layer made of the triaxially oriented Al film. It is possible to increase the diffusion diameter of bonding at the conventional level.

  As a result, the above configuration can improve the bonding strength by increasing the bonding area, improve the thermal shock resistance and the drop impact resistance, and improve the yield at the time of manufacture and the characteristic stability over time. There is an effect that it becomes possible.

  Each embodiment of the present invention will be described below with reference to FIGS.

In the SAW element as the electronic component element of the present invention, as shown in FIG. 2, a plurality of, for example, two IDTs (electronic function units) 2, 2 are formed on the surface of the piezoelectric substrate 1. . Each IDT 2 generates a SAW vibration on the surface of the piezoelectric substrate 1 by an inputted electric signal, detects the propagating SAW, converts it into an electric signal, and outputs it to exert a filter function. is there. In the present embodiment, an example in which two IDTs 2 are formed on the piezoelectric substrate 1 has been described for convenience of explanation and drawing. However, the number is not particularly limited to the above. Examples of the piezoelectric substrate 1 include a piezoelectric substrate such as LiTaO ₃ , LiNbO ₃ , or quartz. On the piezoelectric substrate 1, as shown in FIG. 1, an electrical connection with an external wiring substrate (not shown) is provided. A plurality of electrode pads 3 for achieving electrical continuity and mechanical connection, and routing patterns 4 for connecting the IDTs 2 and the electrode pads 3 are formed.

  Each IDT 2, the first layer 3 a that is the lowermost layer of each electrode pad 3, and each wiring pattern 4 are made of a multilayer structure wiring mainly composed of aluminum (Al) and titanium (Ti), and are vacuum-deposited, sputtering, or plated. Formed by law. In the present embodiment, as the multilayer structure wiring, a Ti layer is disposed on the piezoelectric substrate 1 side and an Al layer is disposed on the Ti layer. Such multi-layered wiring can reduce wiring resistance. The thickness of the first layer 3a of the multilayer wiring is set to about 400 nm in total of the Ti layer and the Al layer. The thickness of the Ti layer may be set to about 10% of the total.

  The electrode pad 3 is formed by laminating an adhesive layer (contact metal) 3b, a stress relaxation layer 3c, a diffusion barrier layer 3d, and a bonding improvement layer 3e in this order on the first layer 3a. For the formation of the adhesive layer 3b, the stress relaxation layer 3c, the diffusion barrier layer 3d, and the bondability improving layer 3e, a vacuum deposition method, a sputtering method or a plating method is used.

  The adhesive layer 3b is intended to improve the bondability between the first layer 3a made of Al and the stress relaxation layer 3c made of Al which is formed separately from the first layer 3a, and is detrimental to bonding. In this embodiment, a NiCr alloy is used, although at least one selected from the group consisting of Ni, Cr, and Ti, which is an element that does not generate a simple phase, may be used.

  The stress relaxation layer 3c has electrical conductivity and may have a lower hardness than the upper and lower layers in contact with the stress relaxation layer 3c, but in the present embodiment, Al is used for the other layers, It is made of Al due to the ease of manufacturing that can also be used as the manufacturing apparatus.

  The diffusion barrier layer 3d only needs to prevent the Au component of the Au bump 5 described later from diffusing into the lower adhesive layer 3b and maintain the bonding strength. In this embodiment, the diffusion barrier layer 3d is made of Ti. It has become. Further, since Ti functions as the diffusion barrier layer 3d, the formation of a brittle alloy called AuAlNiCr can be suppressed, so that the bonding reliability can be further improved. Furthermore, the diffusion barrier layer 3d also has a function as an orientation control layer for controlling, that is, improving the orientation of the bondability improving layer 3e, which is an Al layer thereon.

  The bondability improving layer 3e is an Al layer whose orientation is controlled by the diffusion barrier layer 3d so as to be a triaxially oriented film (also called an epitaxial Al layer or a single crystal Al layer). By making the bondability improving layer 3e in contact with the Au bump 5 a triaxially oriented film, the film hardness of the bondability improving layer 3e can be reduced, and between the bondability improving layer 3e and the Au bump 5 as will be described later. Can improve the bondability.

In addition, as another means for using the bonding property improving layer 3e as a triaxially oriented film, the degree of vacuum at the time of forming the Al layer of the bonding property improving layer 3e can be 10 ⁻⁴ Pa or less. Furthermore, another means is to increase the deposition rate of the Al layer of the bondability improving layer 3e to 2.0 nm / second or more.

  In such a SAW element, since it is used by being attached to a wiring board of a package or a communication device by flip chip bonding using each electrode pad 3, Au bumps 5 are respectively formed on each electrode pad 3 by a ball bonding method. Is formed. The material of the Au bump 5 is Au alone or an alloy containing Au as a main component (Au is 50 mol% or more).

  Hereinafter, an example in which the SAW element is attached to the wiring board 6a of the package 6 by flip chip bonding to form a SAW device as shown in FIG.

  The package 6 is formed in a concave shape (bottomed box shape) by laminating a plurality of ceramics or resins. In other words, the package 6 covers and seals the side walls 6b erected from the periphery of the substantially rectangular plate-like wiring board 6a and the cavity 6c formed by the wiring board 6a and the side walls 6b. The cap part 6d for stopping and the sealing part 6e which seals between each side wall part 6b and the cap part 6d are provided.

  The cap portion 6d is made of a metal plate made of an Fe-Ni alloy, an alloy containing Fe, or the like, or a resin having excellent heat resistance, and the surface thereof is plated as necessary. Examples of the material of the sealing portion 6e include a sealing resin such as a brazing material and an epoxy resin.

  In addition, as shown in FIGS. 4A and 4B, the package 6 includes in-package electrode patterns 6g and 6h on the bottom surface 6f of the wiring board 6a facing the cavity 6c. It is formed of an Al layer or a Ti underlayer / Al layer. The in-package electrode pattern 6g is an input / output pad, and the in-package electrode pattern 6h is a ground pad. In the present embodiment, the in-package electrode patterns 6g and 6h function as external electrodes with respect to the SAW element.

  In addition, in the package 6, a plurality of electrode terminals 6j for electrical connection with the outside are further formed on the outer surface 6i of the wiring board 6a. Each electrode terminal 6j is made of an electrode metal, for example, Al, Au, Ag, Cu, or an alloy or a laminated structure thereof, and is formed by electrode patterns 6g and 6h in the package and wirings (not shown) in the wiring board 6a. Electrically connected.

  Next, a method of mounting such a SAW device in which the Au bumps 5 are respectively attached to the electrode pads 3 on the package 6 will be described. First, as shown in FIGS. 3 and 4, the SAW device is mounted on the package 6 having the in-package electrode patterns 6 g and 6 h formed at positions corresponding to the electrode pads 3 through the Au bumps 5. Put. At this time, in the SAW device, the formation surface of each IDT 2 faces the in-package electrode patterns 6g and 6h, that is, the bottom surface 6f of the wiring board 6a.

Subsequently, at least one of pressing force, heat and ultrasonic waves is applied to the SAW element. As a result, as shown in FIG. 5, a part of the Au bump 5 and a part of the bondability improving layer 3e are fused together to form Au—Al diffusion layers 5a and 5b. The Au—Al diffusion layer 5a is mainly made of Au ₄ Al. The Au—Al diffusion layer 5b is made of Au ₅ Al ₂ . By forming the Au—Al diffusion layers 5 a and 5 b as described above, the SAW device is electrically and mechanically connected by the Au bumps 5 and mounted in the package 6.

  Thereafter, a cap part 6d is attached to the package 6 by the sealing part 6e so as to seal the inside of the cavity part 6c, and a SAW device as an electronic component is obtained.

  In such a SAW element or SAW device, the effect of using the bonding improvement layer 3e, which is the uppermost layer of the electrode pad 3, as a triaxially oriented film was examined based on an X-ray diffraction method (XRD). That is, the relationship between the half width of the X-ray diffraction line (rocking curve) in Al (111) of the bondability improving layer 3e and the amount of plastic deformation indicating the film hardness was examined. The amount of plastic deformation used was an SPM hardness measurement method in which a diamond indenter (needle) was pressed against the film and the indenter trace (plastic deformation amount) remaining on the film was measured. The results are shown in FIG.

  The results in FIG. 6 are data indicating that each of the bonding improvement layers 3e examined is a triaxially oriented film, and is within the scope of the present invention, but it is more preferable that the half width is 2 ° or less. The better the orientation, the smaller the film hardness and the better the bondability.

  When the Ti thickness of the diffusion barrier layer is 10 nm to 50 nm, as will be described later, it becomes uniaxial orientation, in which case the full width at half maximum is 2 ° to 4 °, and the plastic deformation amount is 10 nm to 18 nm. Was found to be greater than in the case of triaxial orientation.

  Next, the thickness of Ti of the diffusion barrier layer is variously changed to 200 nm, 100 nm, 60 nm, 50 nm, and 0, and an Al layer as the bonding improvement layer 3e is formed thereon, and the XRD of the Al layer is formed. The Al (200) pole was investigated. The results are shown in FIGS. 7 shows a case where the thickness of Ti is 200 nm, FIG. 8 shows a case where the thickness of Ti is 100 nm, FIG. 9 shows a case where the thickness of Ti is 60 nm, and FIG. 10 shows a case where the thickness of Ti is 50 nm. Indicates a case where the thickness of Ti is 0, that is, an Al layer is formed on the adhesive layer 3b which is a NiCr layer.

  From these results, when the thickness of the Ti layer of the diffusion barrier layer 3d is 200 nm, 100 nm, and 60 nm, a six-fold symmetrical pattern indicating that the Al layer formed thereon is triaxially oriented (the better the orientation, It can be seen that a clear graphic is obtained (see FIGS. 7 to 9). It can also be seen that when the thickness of the Ti layer is 50 nm, a result showing a ring-shaped figure indicating that the Al layer formed thereon is uniaxially oriented is obtained (see FIG. 10). Furthermore, it can be seen that when the thickness of the Ti layer is zero, no orientation is indicated (see FIG. 11). Further, the above results show that the thickness of the Ti layer of the diffusion barrier layer 3d is preferably 60 nm or more.

  By the way, in the 44th paragraph of Patent Document 1, as a second embodiment, from the element substrate side, a lower electrode made of Al having a thickness of about 100 to 400 nm, an intermediate electrode (a NiCr layer having a thickness of 50 nm, and a thickness of 1 μm). A layer structure is shown having an upper electrode made of about 1 μm of Al) and a Ti layer with a thickness of 50 nm.

  The present invention is different from Patent Document 1 in that the Al layer of the bondability improving layer 3e, which is the uppermost layer of the electrode pad 3, is set as a triaxially oriented film. Since the triaxially oriented Al layer has low film hardness, the diffusion diameter between the Au bump 5 and the Al layer which is the bonding improvement layer 3e of the electrode pad 3 can be widened, and the thermal shock resistance and the drop impact resistance are improved. It becomes possible.

  Therefore, for the SAW element according to the present invention and the conventional example (Patent Document 1), for example, dual SAW filters of 2.5 × 3.0 × 0.65 mmn package are prepared for each of the following specimens, respectively. The drop impact resistance and thermal shock resistance were tested and compared.

  First, those test methods are as follows. The maximum rate of sealing heat reaching 340 ° C., dropping 1.0 m × 30 times, reflow 260 ° C. × 5 times, When the thickness of the Ti layer as the diffusion barrier layer 3d of the SAW element of the present invention is 100 nm, 0/1187, and when the thickness of the conventional Ti layer is 50 nm, the number is 1/1195. Therefore, it can be seen that the present invention is excellent in drop impact resistance and thermal shock resistance because the occurrence of abnormality is suppressed.

  Further, in the present invention, it has been confirmed that there is no problem even when the maximum temperature reached 340 ° C. in the sealing process, dropping 1.0 m × 115 times, and reflowing 260 ° C. × 15 times (0/1189 pieces). It can be seen that it has excellent heat resistance and thermal shock resistance.

  Moreover, the thickness of each layer of the layer structure in the electrode pad 3 of the SAW element of the present invention used in the above test is 387 nm for Al, 200 nm for NiCr, 100 nm for Al, 100 nm for Ti, 100 nm for Ti, and 840 nm for Al from the substrate side. . The thickness of each layer of the layer structure in the electrode pad of the conventional example is 387 nm for Al, 200 nm for NiCr, 100 nm for Al, 50 nm for Ti, and 840 nm for Al from the substrate side.

  In other words, the destruction mode of the bonding between the Au bump and the Al pad layer due to the drop impact and the thermal shock in the conventional example is peeling of the Au bump and the Al pad layer bonding layer. This is because the upper Al layer is hard and the AuAl diffusion diameter is reduced. This inconvenience of peeling is suppressed when the Al layer which is the bondability improving layer 3e of the present invention is a triaxially oriented Al film, because the Al layer is easily plastically deformed from the above results.

  Next, a communication device using the SAW element or the SAW device described in the above embodiment will be described with reference to FIG. The communication device 100 includes an antenna 101, an antenna sharing unit / RFTop filter 102, an amplifier 103, an Rx interstage filter 104, a mixer 105, a 1st IF filter 106, a mixer 107, and a 2nd IF filter 108 as a receiver side (Rx side) that performs reception. 1st + 2nd local synthesizer 111, TCXO (temperature compensated crystal oscillator) 112, divider 113, and local filter 114 are provided.

  It is preferable to transmit from the Rx interstage filter 104 to the mixer 105 by each balanced signal in order to ensure balance, as shown by the double line in FIG.

  The communication device 100 shares the antenna 101 and the antenna sharing unit / RFTop filter 102 as a transmitter side (Tx side) that performs transmission, and also includes a TxIF filter 121, a mixer 122, a Tx interstage filter 123, and an amplifier. 124, a coupler 125, an isolator 126, and an APC (automatic power control) 127.

  As the Rx interstage filter 104, the 1stIF filter 106, the TxIF filter 121, and the Tx interstage filter 123, the SAW element or the SAW device described in the present embodiment can be preferably used.

  The SAW element or SAW device according to the present invention has excellent characteristics that it can be miniaturized and can improve yield and stability of electrical characteristics over time. Therefore, the communication device of the present invention having the SAW element or SAW device can be reduced in size, and can be reduced in cost and stability over time.

  In the above-described embodiment, an example in which a SAW element is used as an electronic component element has been described. However, the present invention can be applied as long as bonding using Au bumps 5 is used. For example, in a semiconductor element (electronic function unit) The present invention can also be applied to a QFP (Quad Flat Pack-type) packaged with an integrated circuit (LSI).

  In the SAW element and the SAW device described in the above embodiment, the Au bump 5 is first formed on the electrode pad 3, but the in-package electrode patterns 6 g and 6 h that serve as external electrodes for the SAW element are given. The Au bump 5 may be provided first.

  The electronic component element, the electronic component, and the communication device of the present invention are excellent in the yield and the stability over time of the electrical characteristics while being reduced in size, and thus can be suitably used in the communication field such as a mobile phone.

It is principal part sectional drawing of the SAW element as an electronic component element of this invention. It is a top view of the said SAW element. It is a schematic sectional drawing of the SAW device of this invention. The package of the said SAW device is shown, (a) is a principal part top view, (b) is principal part sectional drawing. It is principal part sectional drawing of the electrode pad and Au bump in the said SAW device. In the said SAW device, it is a graph which shows the relationship between the half value width of the diffraction line (rocking curve) by X-ray diffraction which shows the orientation of Al layer (111) of an electrode pad, and the plastic deformation amount which shows the hardness of the said Al layer. is there. It is a graph which shows the measurement result of the Al (200) pole by XRD of the said Al layer in case the thickness of Ti of the lower layer of the said Al layer is 200 nm. It is a graph which shows the measurement result of the Al (200) pole by XRD of the said Al layer in case the thickness of Ti of the lower layer of the said Al layer is 100 nm. It is a graph which shows the measurement result of the Al (200) pole by XRD of the said Al layer in case the thickness of Ti of the lower layer of the said Al layer is 60 nm. It is a graph which shows the measurement result of the Al (200) pole by XRD of the said Al layer in case the thickness of Ti of the lower layer of the said Al layer is 50 nm. It is a graph which shows the measurement result of the Al (200) pole by XRD of the said Al layer in case the thickness of Ti of the lower layer of the said Al layer is 0 nm. It is a principal part block diagram of the communication apparatus of this invention.

Explanation of symbols

1: Piezoelectric substrate (substrate)
2: IDT (Electronic Function Unit)
3: Electrode pad 3e: Bondability improving layer (triaxially oriented Al film)
5: Au bump

Claims (8)

A substrate,
An electronic function unit formed on the substrate;
An electrode pad connected to the electronic function unit;
An Au bump formed on the electrode pad,
An electronic component element, wherein an uppermost layer in contact with the Au bump in the electrode pad is made of a triaxially oriented Al film.   The electronic component element according to claim 1, wherein the electrode pad is provided with a diffusion barrier layer below the uppermost layer.   3. The electron according to claim 2, wherein the electrode pad further includes a lower electrode layer, an adhesive layer, and a stress relaxation layer from the substrate side between the substrate and the diffusion barrier layer. Component element.   4. The electronic component element according to claim 2, wherein the diffusion barrier layer is made of Ti.   5. The electronic component element according to claim 2, wherein the diffusion barrier layer has a layer thickness of 60 nm or more.   6. The electronic component element according to claim 1, wherein the substrate is a piezoelectric substrate, and the electronic function unit is a comb-shaped electrode unit formed on the piezoelectric substrate. The electronic component element according to any one of claims 1 to 6,
An electronic component comprising: a package having an external electrode formed at a position corresponding to the Au bump. A communication device comprising the electronic component element according to any one of claims 1 to 6 or the electronic component according to claim 7.

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