JP2003086625A - Electronic part element and electronic part device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electronic part element whose yield can be improved and, to provide an electronic part device using the element. SOLUTION: An element electrode and a ground electrode 8 as an electrode pad which is electrically connected with the element electrode are formed on a piezoelectric substrate 3. An upper electrode 11 connected to an Au bump 10 and an intermediate electrode 12 formed between the ground electrode 8 and the upper electrode 11 are formed on the ground electrode 8. The upper electrode 11 is brought into contact with the intermediate electrode 12, is brought into contact with a first layer 11a constituted of an Al alloy and the Au bump 10, and has the two layer structure of a second layer 11b constituted of Al.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic component suitable for face-down mounting in which a metal bump formed on an element substrate of an electronic component element is pressed against an electrode pattern of a package made of ceramic or the like or a circuit board to connect. The present invention relates to an element and an electronic component device having the element.

[0002]

2. Description of the Related Art In recent years, with the downsizing and height reduction of electronic component devices, as a method of connecting the electrode pads of the electronic component elements and the electrode patterns of the package used in the electronic component device, instead of connecting by wires, electronic components are used. A face-down type connection has been developed in which the functional surface of a component element is opposed to the connection surface of a package and directly mounted.

In connection with the electrode pad of the electronic component element and the electrode pattern of the package by such a face-down method, gold (Au) is used because of easy connection and dimensional controllability.
Bumps are often used. As described above, the electronic component device is manufactured by attaching the cap portion (lid portion) to the opening of the package to which the electronic component elements are connected by the face-down method by hermetically sealing with solder or the like.

A general structure of a surface acoustic wave device as an example of an electronic component device by face-down mounting using Au bumps as described above will be described below. In a surface acoustic wave element used for a surface acoustic wave device, when it is necessary to form a comb-shaped electrode with a film thickness of about 0.1 μm to 0.5 μm on a substrate, an electrode pad connected to the comb-shaped electrode is used. The film thickness can be formed only to the same extent as the film thickness of the comb-shaped electrode. This is because the electrode pad is formed simultaneously with the comb-shaped electrode by the photolithography method and the etching method or the lift-off method.

Thus, the film thickness is 0.1 μm to 0.5 μm.
If an Au bump is formed directly on a certain level of the electrode pad and the surface acoustic wave element is mounted face down on the package via the Au bump, the strength of the electrode pad is weak and the electrode pad is peeled off, resulting in sufficient bonding. The problem is that strength cannot be obtained.

Therefore, the conventional surface acoustic wave element disclosed in Japanese Patent Laid-Open No. 2001-15540 is, as shown in FIG.
On the electrode pad 22 such as the ground electrode and the input / output electrode formed on the piezoelectric substrate 21, Al having a film thickness of about 1 μm or substantially Al-1 was formed by the lift-off deposition method.
It has an upper electrode 23 made of a wt% Cu alloy together with an intermediate electrode 24 made of NiCr alloy or Ti, which has a good adhesive strength with Al. Al indicates aluminum having a purity of almost 100%, and Al-1 wt% Cu alloy is 1 wt% Cu in an AlCu alloy of aluminum and copper.
In other words, it means that it contains 0.3 atom% of Cu.

As a result, in the above-described surface acoustic wave device, the thickness on the electrode pad 22 is set to the intermediate electrode 24 and the upper electrode 2.
3 by ensuring that the electrode pad 22 is
Sufficient bonding strength of the package container 28 to the package electrode 27 via the bump electrode 26 containing u as a main component can be obtained.

[0008]

However, when the upper electrode 23 is a single layer made of Al or an AlCu alloy, there are the following problems in the prior art.

Since Al is softer than an AlCu alloy compared with an AlCu alloy, non-bonding failure of the bump electrode 26 does not occur in the bump bonding process. Vickers hardness, which is an index of hardness, is Al (30) <Au (80) <Al-1 wt% Cu.
It is (200) (hardness is shown in parentheses).

However, Au / Al interdiffusion is likely to proceed due to the heat during the sealing of the cap portion, and Table 1 (Problem occurrence rate when the thickness of the upper electrode 23 is 1 μm (n = 200 pc)
As shown in s)), intermetallic compounds are easily formed. Therefore, cracks may occur in the piezoelectric substrate 21 below the bump electrodes 26.

As shown in Table 1, in the intermetallic compound formation surface, when the upper electrode 23 on the electrode pad 22 was made of Al-Cu alloy, it was increased by about 25% in the case of Al.

On the contrary, the AlCu alloy does not cause cracks in the piezoelectric substrate 21, but in the bump bonding process, about 10% of non-bonding defects of the bump electrodes 26 occur as shown in Table 1.

[0013]

[Table 1]

In Table 1, * indicates an Au / Al intermetallic compound formed under the bump electrode 26. (1) Au / Al intermetallic compound formed under the bump electrode 26: intermetallic compound formation → volume expansion [the volume of the compound Al ₂ Au is about twice that of (Al × 2 + Au)] → stress accumulation → cracking The mechanism has cracks. Therefore, it is effective to prevent crack formation by reducing the area where the intermetallic compound is formed. However, formation of some intermetallic compound is indispensable for joining.

[0015]

In order to solve the above-mentioned problems, an electronic component element of the present invention includes an element substrate, an element electrode formed on the element substrate, and an electrical connection with the element electrode. And an electrode pad, an upper electrode formed on the electrode pad and connected to a metal bump, and an intermediate electrode formed between the electrode pad and the upper electrode. It is characterized in that the upper electrode has a two-layer structure of a first layer made of an Al alloy in contact with the intermediate electrode and a second layer made of Al in contact with the metal bump.

According to the above structure, the uppermost layer of the upper electrode is A
Since the surface of the electrode pad can be apparently made softer than the metal bump by the second layer by disposing the Al alloy at the interface with the intermediate electrode, the adhesion to the metal bump can be improved.

Further, in the above structure, since the Al alloy layer suppresses the diffusion of the metal of the metal bump in the electrode pad, the formation area area of the intermetallic compound formed by Al and the metal of the metal bump is small. Therefore, partial stress concentration due to the volume change of the intermetallic compound can be relaxed.

In the electronic component element, the material of the metal bump is Au, the intermediate electrode is Ti, Cr,
At least one metal selected from NiCr alloys, and the Al alloy is an alloy of Al and a migration-inhibiting metal selected from at least one selected from the group consisting of Cu, W, Ti, Cr, Ta, and Si. It is preferable.

According to the above construction, by setting the metal bump, the intermediate electrode and the Al alloy respectively as described above, it is possible to improve the adhesion to the metal bump and to alleviate the partial stress concentration.

In the electronic component element, the concentration of the migration-inhibiting metal in the Al alloy is preferably within the range of 0.15 atom% to 0.45 atom%.

According to the above structure, the concentration of the migration-inhibiting metal is set to 0.15 atom% to 0.45 atom%, so that partial stress concentration can be more reliably relaxed.

In the electronic component element, the thickness of the Al layer is preferably 1% or more and 75% or less of the thickness of the upper electrode, and more preferably 5% or more and 50% or less.

According to the above structure, by setting the film thickness of the Al layer as described above, it is possible to improve the adhesion with the metal bumps and alleviate the partial stress concentration.

In the above electronic component element, the element substrate and the element electrode may be for a surface acoustic wave element. According to the above configuration, it is possible to reduce partial stress concentration on the element substrate, reduce the occurrence of cracks on the element substrate, and reduce the characteristic deterioration of the surface acoustic wave element.

In the electronic component element, it is desirable that the upper electrode and the intermediate electrode are collectively formed by a lift-off method. According to the above configuration, the upper electrode and the intermediate electrode are collectively formed by the lift-off method, so that the formation of the upper electrode and the intermediate electrode can be simplified.

In order to solve the above problems, an electronic component device of the present invention is characterized in that the electronic component element described in any one of the above is housed in a package by face-down mounting.

According to the above structure, the non-bonding failure of the metal bump due to the improved adhesion with the metal bump used for face-down mounting in the package is reduced, and the partial stress concentration is alleviated to crack the element substrate. Since the electronic component elements whose generation is suppressed are housed in the package by face-down mounting, the characteristics are excellent and the yield can be improved.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION A surface acoustic wave device as an electronic component element and a surface acoustic wave device as an electronic component device having the same according to an embodiment of the present invention will be described with reference to FIGS.
The explanation is based on the following. 2 is a plan view of the surface acoustic wave device, FIG. 3 is a sectional view of a surface acoustic wave device in which the surface acoustic wave device is housed in a package, and FIG. 1 is an enlarged bump portion of the surface acoustic wave device. It is a figure.

As shown in FIGS. 1 and 3, a surface acoustic wave device 1 is provided.
The surface acoustic wave device 2 is mounted facedown in a package 9 made of ceramic. The package 9 includes a bottomed box-shaped package body 9e having an internal space capable of accommodating the surface acoustic wave element 2.

As shown in FIG. 2, the surface acoustic wave element 2 has
Piezoelectric substrate 3 of lithium tantalate and A on piezoelectric substrate 3
a thin film having a film thickness of about 100 nm to 400 nm made of 1 through the IDTs 4a and 5a of the surface acoustic wave filters 4 and 5 and the reflectors 4b and 5b, the input electrode 6 and the output electrode 7, and the ground electrode 8 via the intermediate electrode 12. It is composed of the formed upper electrode 11 (FIG. 1).

Among these electrodes, the IDTs 4a, 5a and the reflectors 4b, 5b of the surface acoustic wave filters 4, 5 are element electrodes for the surface acoustic wave element 2 to function, and the input electrode 6, the output electrode 7, The ground electrode 8 is an electrode pad for electrically and physically connecting the element electrode to the circuit board or package.

On the output electrode 7 and the ground electrode 8, the film thickness is
For example, 200 nm Ti or NiCr alloy film (Ni
An upper electrode 11 having a film thickness of about 1 μm is formed with an intermediate electrode 12 made of a Cr alloy film having a Cr concentration of 25% by weight) sandwiched therebetween.

In the surface acoustic wave device 1, the upper electrode 1
1 is electrically and mechanically connected to the electrode patterns 9a and 9b made of Au formed on the inner bottom surface of the package body 9e by Au bumps (metal bumps) 10, respectively. The outer surface of the package body 9e has A
The external electrodes 9c, 9d made of u are the electrode patterns 9a,
9b are provided so as to be connected to each.

The upper electrode 11 is in contact with the intermediate electrode 12, and the first layer 11a made of an Al alloy and the Au bump 1 are formed.
It has a two-layer structure in which a second layer 11b which is in contact with 0 and is made of pure Al is laminated on each other. Therefore, the intermediate electrode 12, the first layer 11a, and the second layer 11b are laminated in this order on, for example, the ground electrode 8 as an electrode pad.

Next, a method of manufacturing the surface acoustic wave device according to the embodiment of the present invention will be described. First, as shown in FIG. 2, a comb-shaped electrode of Al or Al alloy having a film thickness of about 300 nm is formed on the piezoelectric substrate 3 by vacuum deposition or sputtering, photolithography, etching or lift-off. By patterning into a predetermined shape, the IDTs 4a and 5a of the surface acoustic wave filters 4 and 5 and the reflectors 4b and 5b, and the input electrode 6, which is an electrode pad, the output electrode 7 and the ground electrode 8 are formed.

Then, as shown in FIG. 1, on the input electrode 6 and the output electrode 7 and the ground electrode 8, vacuum deposition using a lift-off method was performed to form a film having a thickness of about 200 nm and 25 wt% of Cr.
The intermediate electrode 12 made of contained NiCr is formed, and subsequently, A having a predetermined film thickness is formed on the intermediate electrode 12 by continuous vapor deposition.
First layer 1 of the upper electrode 11 made of 1-1 wt% Cu alloy
1a is formed, and the second layer 1 of the upper electrode 11 made of Al having a predetermined thickness is formed on the first layer 11a by continuous vapor deposition.
1b is formed. Therefore, the intermediate electrode 12 and the upper electrode 1
1 are collectively formed by the lift-off method. At this time, the film thickness of the upper electrode 11 including the first layer 11a and the second layer 11b is set to about 1 μm.

Au bumps 10 are formed on the upper electrodes 11 thus formed by a ball bonding method. Specifically, a ball formed at the tip of the Au wire is pressed onto the upper electrode 11 while applying ultrasonic waves, and then the Au wire is cut from the base end of the ball to remove the Au wire.
The bump 10 is formed.

As shown in FIG. 3, the surface acoustic wave element 2 formed through the above steps has its upper electrode 11 forming surface formed on the inner bottom surface of the package body 9e. The Au bumps 10 are made to face the 9a and 9b.

Next, while applying ultrasonic waves and heat to the surface acoustic wave element 2, the surface acoustic wave element 2 is pressed toward the inner bottom surface of the package body 9e, and the surface acoustic wave element 2 is pressed.
And the electrode patterns 9a and 9b are connected to each other (also referred to as face-down mounting or flip-chip method).

Next, the surface acoustic wave device 1 is completed by covering the opening of the package body 9e with the cap 9f and hermetically sealing the space between the opening and the cap 9f with solder or the like. At the time of such airtight sealing, A
Heat for hermetic sealing is also applied to the u-bump 10, the upper electrode 11, the intermediate electrode 12, the ground electrode 8 and the like, and the piezoelectric substrate 3 portion on which it is formed.

In such a surface acoustic wave device 1, as shown in Table 2, the film thickness ratio between the first layer 11a made of AlCu alloy and the second layer 11b made of Al in the upper electrode 11 is changed variously. 200 surface acoustic wave devices 1 (200 pcs) were prepared.

[0042]

[Table 2]

The film thickness ratio shown in Table 2 above is Al film thickness / AlC
u shows the film thickness, K shows the crack occurrence rate (%), and B shows the bump non-stick occurrence rate (%).

As the AlCu alloy, an alloy containing 1% by weight (wt)% (0.3 atom%) of Cu in the AlCu alloy was used. The Cu content in the AlCu alloy depends on the second layer 11
From the viewpoint of affinity with b and hardness, 0.5 wt% to 1.
In the range of 5 wt%, in other words, the range of 0.15 atom% to 0.45 atom% is preferable in terms of atom%.

The crack occurrence rate (%) and the Au bump 10 (metal bump) non-attachment occurrence rate (%) on the piezoelectric substrate 3 were measured, and Table 2 shows the measurement results. As is clear from the results of Table 2 and Table 1 above, the upper electrode 11
Shows that the two-layer structure of AlCu alloy and Al is better than the conventional single layer alone. The ratio of the Al film thickness to the total film thickness of the Al / AlCu alloy is 1% to 75%.
However, it is found that 5% to 50% is more preferable.

In the present invention, the uppermost second layer 11b of the upper electrode 11 is made of Al, and the first layer 11a on the interface side with the intermediate electrode 12 is made of Al alloy. The surface of the first layer 11b is apparently softer than Au by the second layer 11b, so that the adhesion with the Au bumps 10 is improved, and the first layer 11a which is an Al alloy layer.
The Au into the ground electrode 8 as an electrode pad.
It was found that since the diffusion of Al is suppressed, the area where the intermetallic compound is formed becomes smaller, and the stress concentration due to the partial volume change can be relaxed.

As a result, according to the present invention, the yield of the Au bump bonding process can be improved from 90% to almost 100%, and the crack generation of the piezoelectric substrate 3 under the Au bump 10 can be completely prevented. Therefore, the surface acoustic wave device 1 can be manufactured under stable conditions that are free from defects in the manufacturing process, and the surface acoustic wave device 1 having high reliability can be provided.

In the above embodiment, the piezoelectric substrate 3 made of lithium tantalate was used as the element substrate, but the present invention is not limited to this. For example, insulation provided with a lithium niobate or zinc oxide film. The same effect can be obtained with a piezoelectric substrate such as a substrate, crystal, or Langasite.

In the above embodiment, an example in which an AlCu alloy is used as the Al alloy of the first layer 11a has been given, but as the metal other than Al contained in the Al alloy,
Not limited to Cu, migration (mi
gration) Any inhibitory metal such as W, T
Metals including i, Cr, Ta, Si, and Cu can be used in combination.

Further, in the above-mentioned embodiment, the example in which NiCr containing 25% by weight of Cr is used as the intermediate electrode 12 has been described, but the present invention is not limited to the above, and Ti and Cr may be used. Can be used.

In the above embodiment, the surface acoustic wave element 2 is used as the electronic component element, but it is face-down mounted using the metal bump such as the Au bump 10. If so, the present invention can be applied to achieve the same effect.

[0052]

As described above, the electronic component element of the present invention is a face-down mounted electronic component element.
An intermediate electrode and an upper electrode are formed on an electrode pad of an element substrate, and the upper electrode has a two-layer structure of a first layer made of an Al alloy in contact with the intermediate electrode and a second layer made of Al in contact with a metal bump. It is a structure having.

Therefore, in the above structure, the uppermost layer of the upper electrode is made of Al, and the Al alloy is arranged at the interface with the intermediate electrode, whereby the electrode pad surface can be made softer than the metal bump by the second layer. Therefore, the adhesion with the metal bump is improved, and since the Al alloy layer suppresses the diffusion of the metal of the metal bump in the electrode pad, the area where the intermetallic compound is formed becomes small and the partial volume is reduced. Stress concentration due to changes can be relaxed.

As a result, in the above structure, the adhesion to the metal bumps is improved to reduce the occurrence of non-adhesion of the metal bumps, the yield in the bump bonding process can be improved as compared with the conventional case, and the stress concentration can be relaxed. There is an effect that it is possible to suppress the occurrence of cracks in the lower element substrate.

[Brief description of drawings]

FIG. 1 is an enlarged sectional view of an essential part of a surface acoustic wave device according to an embodiment of the present invention.

FIG. 2 is a schematic plan view of a surface acoustic wave element of the surface acoustic wave device.

FIG. 3 is a schematic sectional view of a surface acoustic wave device including the surface acoustic wave element.

FIG. 4 is an enlarged cross-sectional view of a main part of a conventional surface acoustic wave device.

[Explanation of symbols]

3 Piezoelectric substrate (element substrate) 8 electrode pads 10 metal bumps 11 Upper electrode 11a First layer 11b Second layer 12 Intermediate electrode

Claims (8)

[Claims] 1. An element substrate, an element electrode formed on the element substrate, an electrode pad electrically connected to the element electrode, and an upper electrode formed on the electrode pad and connected to a metal bump. A face-down mounted electronic component element having the electrode pad and an intermediate electrode formed between the upper electrode, wherein the upper electrode is a first layer made of an Al alloy in contact with the intermediate electrode, An electronic component element having a two-layer structure of a second layer made of Al in contact with the metal bump. 2. The material of the metal bump is Au, the intermediate electrode is at least one kind of metal among Ti, Cr and NiCr alloys, and the Al alloy is Cu, W, Ti and C.
2. The electronic component element according to claim 1, which is an alloy of Al and a migration suppressing metal selected from at least one selected from the group consisting of r, Ta, and Si. 3. The concentration of the migration-inhibiting metal in the Al alloy is 0.15 atomic% to 0.45 atomic%.
The electronic component element according to claim 2, which is within the range up to. 4. The thickness of the Al layer is 1% of the thickness of the upper electrode.
The electronic component element according to any one of claims 1 to 3, wherein the content is 75% or less. 5. The film thickness of the Al layer is 5% of the film thickness of the upper electrode.
The electronic component element according to any one of claims 1 to 4, wherein the content is 50% or more. 6. The electronic component element according to claim 1, wherein the element substrate and the element electrode are for a surface acoustic wave element. 7. The upper electrode and the intermediate electrode are collectively formed by a lift-off method.
The electronic component element according to any one of 1. 8. An electronic component device in which the electronic component element according to any one of claims 1 to 7 is housed in a package by face-down mounting.