JPH08274571A - Diamond base material and element for surface acoustic wave element - Google Patents

Abstract

PURPOSE: To improve adhesion on a diamond surface by forming an Al electrode part with an Al including at least one or more specified wt.% elements out of prescribed elements such as Si, etc. CONSTITUTION: The Al electrode part formed on a diamond layer is formed with the Al including at least one or more kinds of 0.1-5.0wt.% element out of Si, Sc, Ti, Cr, Mn, Ni, Nb, Mo, Pd, Ta and W. In such a case, high adhesion is obtained by applying coupling with added metal or an Al atom, and simultaneously, coupling with diamond carbon. Also, since added quantity is selected so as not to impair element characteristic, the peeling of an electrode part when wire bonding is applied is controlled, which enables mounting on a package.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface acoustic wave device or a diamond substrate for a surface acoustic wave device having improved adhesion between a diamond layer and an aluminum (Al) metal electrode.

[0002]

2. Description of the Related Art A surface acoustic wave device using a laminated structure of diamond and a piezoelectric material has been developed as a device that can be applied at high frequencies (Japanese Patent Laid-Open Nos. 64-62911 and 3-198412).

A surface acoustic wave device using this diamond film or diamond layer as a substrate is manufactured, for example, as follows.

First, a diamond film is formed on a substrate such as Si by vapor phase synthesis. The surface of this diamond film is smoothed by polishing. Further, this diamond film having a smooth surface is used as a substrate, and an excitation electrode portion and a piezoelectric thin film are formed thereon.

Here, the excitation electrode portion is usually composed of an electrode portion having a comb shape or the like which actually acts, and a pad electrode portion for wire bonding for coupling with a package or the like.

Further, as a material for forming the electrode portion, Al, Al-Cu, Al-Sc, etc. have been used because they are less likely to deteriorate the characteristics of the surface acoustic wave element.

[0007]

However, Al,
The electrode part using Al-Cu, Al-Sc, etc. has a problem that the pad electrode part is easily separated from the diamond surface during the wire bonding process. Therefore, the wire bonding between the package and the pad electrode part of the element is difficult. There was a problem that it would be difficult.

Therefore, it is desired to develop a material for the excitation electrode portion having sufficient adhesion to the diamond surface acoustic wave which can withstand the steps such as wire bonding without deteriorating the characteristics of the surface acoustic wave element. .

[0009]

Means for Solving the Problems In view of the above demands, the inventors of the present invention have diligently studied and made Al or Al-Cu, Al-
It was found that the above problems can be solved by adding various metals capable of forming a strong bond with both substances in order to increase the adhesion between the metal electrode layer such as Sc and the diamond layer, and the present invention was completed. Came to do.

That is, the diamond substrate for a surface acoustic wave device according to the present invention has at least a diamond layer and Al.
In a substrate for a surface acoustic wave device having an electrode portion, the Al electrode portion formed on the diamond layer is made of Si, S
c, Ti, Cr, Mn, Ni, Nb, Mo, Pd, T
at least one element of a and W is 0.1 to 0.1
It is characterized by being formed of Al containing 5.0% by weight.

Further, the diamond base material for a surface acoustic wave element according to the present invention is a surface acoustic wave element base material having at least a diamond layer and an Al electrode portion, wherein the Al electrode portion formed on the diamond layer is Si, Sc, T
0.1 to 5.0 wt% of at least one element of i, Cr, Mn, Ni, Nb, Mo, Pd, Ta and W, and 0.1 to 5.0 wt% of Cu. It is characterized by being formed of Al containing Al.

The surface acoustic wave element base material for a surface acoustic wave device according to the present invention is a surface acoustic wave device base material having at least a diamond layer and an Al electrode part, wherein the Al electrode part formed on the diamond layer is: Si, Ti, C
0.1 to 5.0% by weight of at least one element out of r, Mn, Ni, Nb, Mo, Pd, Ta and W,
It is characterized by being formed of Al containing 0.1 to 5.0% by weight of Sc.

Further, the diamond substrate for a surface acoustic wave device according to the present invention is characterized in that the diamond layer is a vapor phase synthetic diamond.

The surface acoustic wave device according to the present invention is
At least diamond layer, piezoelectric layer, and excitation Al
In a surface acoustic wave device having an electrode portion, the Al electrode portion formed on the diamond layer is made of Si, Sc, T
It is characterized in that it is formed of Al containing 0.1 to 5.0% by weight of at least one element of i, Cr, Mn, Ni, Nb, Mo, Pd, Ta and W.

The surface acoustic wave device according to the present invention is
At least diamond layer, piezoelectric layer, and excitation Al
In a surface acoustic wave device having an electrode portion, the Al electrode portion formed on the diamond layer is made of Si, Sc, T
0.1 to 5.0 wt% of at least one element of i, Cr, Mn, Ni, Nb, Mo, Pd, Ta and W, and 0.1 to 5.0 wt% of Cu. It is characterized by being formed of Al containing Al.

Further, the surface acoustic wave device according to the present invention is a surface acoustic wave device having at least a diamond layer, a piezoelectric layer, and an exciting Al electrode part, and the Al electrode part formed on the diamond layer. But Si, Ti,
0.1 to 5.0% by weight of at least one element of Cr, Mn, Ni, Nb, Mo, Pd, Ta, W
And Al containing 0.1 to 5.0% by weight of Sc.

The surface acoustic wave device according to the present invention is
The diamond layer is characterized in that it is a vapor phase synthetic diamond provided on a Si substrate.

Further, in the surface acoustic wave device according to the present invention, the piezoelectric material is ZnO or Li, Na, K, Rb,
It is characterized by being an insulating ZnO containing at least one element of Mn and Cu.

Further, the surface acoustic wave device according to the present invention is characterized in that the piezoelectric body is LiNbO ₃ .

The present invention will be described in more detail below.

(Al Electrode Portion) In the present invention, the shape of the Al electrode portion is not particularly limited. Generally, it is desirable that the pad electrode portion for wire bonding and the comb-shaped electrode portion that performs an action such as excitation are formed.

In the present invention, the method for forming the Al electrode portion is not particularly limited. For example, DC sputtering method,
Known methods such as an RF sputtering method, an ion beam sputtering method, a vacuum vapor deposition method and an ion plating method can be preferably used.

In the present invention, the method of adding the predetermined metal is not particularly limited. For example, in the sputtering method,
A method of mixing a predetermined amount of a predetermined metal in the target metal can be preferably used.

The quantification of the metal added to the Al electrode portion can be carried out by metal analysis of a part of the formed Al metal electrode portion. For example, the atomic absorption method can be preferably used.

In the present invention, the added metal is Al
It does not need to be uniformly distributed in the electrode part. In particular, in the vicinity of the interface with diamond, the added metal may be present at an average concentration or higher.

Further, in the present invention, the shape of the comb-shaped electrode for the operation is not particularly limited.

Also, the shape of the pad electrode portion for wire bonding is not particularly limited and can be selected depending on the conditions of wire bonding processing. For example, the size of the wire for wire bonding, the material of the wire, the number of bondings, and the like.

Further, in the present invention, the thickness of the Al electrode portion is not particularly limited. As long as it does not affect the device characteristics, for example, the comb electrode may have a thickness of 100 angstroms or more and 2000 angstroms or less, and the pad electrode may have a thickness of 500 angstroms or more.

(Additional Metal) In the present invention, Al, Al
The types of metal elements added to the electrode material of -Cu, Al-Sc are Si, Sc, Ti, Cr, Mn, Ni, Nb,
It is at least one kind of element among Mo, Pd, Ta, and W.

In the present invention, the reason why the added metal increases the adhesiveness between diamond and Al can be considered.

One of the materials that provides the strongest adhesion is that the added metal forms a bond with the Al atom and simultaneously with the diamond carbon. The presence of this bond is particularly likely near the interface of both materials.
For example, it is known that carbon, Si, Ti, W, etc. form a compound. In addition, a bond between an oxide existing on the surface and a metal (for example, Mo-O-C), and a covalent bond formation between a metal and carbon (for example, Cr-C) are also considered.

Therefore, in the present invention, it can be presumed that the effect of improving the adhesion by the added metal is a phenomenon mainly in the vicinity of the interface between the diamond and the Al electrode.

Therefore, the amount of addition is as small as about 0.01 to 5%, so that the characteristics of the device are not significantly impaired.

(Diamond Layer) In the present invention, the diamond film may be either single crystal diamond or polycrystalline diamond.

The method for obtaining the diamond film is not particularly limited. More specifically, single crystal diamond may be used, or a diamond film may be vapor-grown on another material (base material) and synthesized. Further, it may be an epitaxial film.

The base material is not particularly limited and can be selected depending on the use of the surface acoustic wave device. For example, a semiconductor such as Si, metal, glass, ceramics or the like can be used.

In the present invention, the method for forming the diamond film is not particularly limited, and known methods can be preferably used. For example, there are a CVD (chemical vapor deposition) method, a microwave plasma CVD method, a PVD (physical vapor deposition) method, a sputtering method, an ion plating method, a plasma jet method, a flame method, a filament method and the like.

(Piezoelectric Body) In the present invention, there is no particular limitation on the piezoelectric body that can be used. Various single crystals and ceramics can be preferably used as the piezoelectric body. For example, ZnO or metal-doped ZnO, or LiNbO
₃ etc. can be preferably used.

The method for forming the piezoelectric film is not particularly limited,
Known methods can be used. For example, there are a CVD (chemical vapor deposition) method, a microwave plasma CVD method, a PVD (physical vapor deposition) method, a sputtering method, an ion plating method and the like.

(Wire Bonding) The wire bonding method that can be used in the present invention is not particularly limited. Generally used wedge bonding, ball bonding, etc. can be used.

It can be selected depending on the wire diameter of the wire used, the material, the shape of the pad electrode portion, the number of bondings, and the like.

(Evaluation of Adhesion) At the time of wire bonding, the pad electrode portion may be separated from the diamond surface acoustic wave due to the force applied to the pad electrode portion, and the adhesion strength may be more than that value. is necessary.

Therefore, in order to evaluate the adhesion between the diamond film and the Al electrode portion, various methods depending on the wire bonding method can be applied.

For example, an evaluation method according to tensile adhesion strength, peel adhesion strength, impact adhesion strength (JIS handbook adhesion, Japanese Standards Association) or the number of times peeling occurs during wire bonding is evaluated. The method etc. which do can be used.

In the present invention, 100 solid pad electrode portions (size 400 μm × 4
A method of actually performing wire bonding on a wedge bonder (wire size: 25 μmφ, Al (1 wt% Si)) to 00 μm, thickness: 0.6 μm, and calculating the wire bonding failure rate can be suitably used.

Further, it can be evaluated by measuring the breaking strength of the bonded wire by a tensile test (for example, MIL STD 883C).

In the breaking strength of the bonded Al wire according to the present invention by the above tensile test, it is desirable that at least 50% or more is 3 g or more,
It is more preferably 70% or more, and particularly preferably 90% or more.

Similarly, in the breaking strength of the bonded Au wire according to the present invention as measured by a tensile test, 50% or more is preferably 4 g or more, more preferably 70% or more, and particularly preferably. 90% or more.

(Element Loss) In the present invention, it is preferable to evaluate the influence on the element characteristics, but the method is not particularly limited. For example, it is possible to form a surface acoustic wave element filter and evaluate the element loss.

In the present invention, it is desirable that the element loss does not change at all by adding a metal to the AL electrode portion. If the amount of metal added is too large, the element loss increases.

[0051]

The diamond base material and element for surface acoustic wave devices according to the present invention use Al to which a metal that increases the adhesion to the diamond layer is added to the electrode material. The addition amount is selected so as not to impair the device characteristics. Therefore,
The peeling of the electrode portion at the time of wire bonding is controlled, and it becomes possible to mount the electrode portion on the package.

[0052]

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to this.

Microwave plasma CVD on a Si substrate
In the method, a diamond film is formed under the following conditions.

Conditions for diamond film formation Microwave power: 150 W Reaction gas: CH ₄ : H ₂ = 2: 100 Gas pressure: 40 mTorr Film formation temperature: 800 ° C. Film thickness: 35 μm The obtained diamond film surface was polished to form a diamond film. The thickness is set to 20 μm and is used as a surface acoustic wave device substrate.

Further, an electrode layer is formed on the substrate by DC sputtering. The electrode material used here is shown in Table 1.
Is shown in.

Electrode layer forming conditions DC power: 2.5 kW Film forming rate: 50 Å / sec Sputtering gas: Ar gas pressure: 10 mTorr Film forming temperature: room temperature Film thickness: 500 Å The obtained electrode layer was formed by photolithography. To form a comb-shaped electrode portion having a gap of 1.5 μm and having a pad electrode portion.

A ZnO (containing 2 atomic mol% of Li) piezoelectric layer was further formed on the obtained substrate by a sputtering method.

ZnO film formation conditions RF power: 150 W Sputtering gas: Ar: O ₂ = 80: 20 Gas pressure: 50 mTorr Film formation temperature: 300 ° C. ZnO directly above the pad electrode portion of the obtained device was subjected to photolithography. To remove the pad electrode portion.

Further, an Al (1 wt% Si) electrode material having a film thickness of 5500 Å is further stacked on the portion directly above the pad electrode portion to obtain an element.

The element obtained is used as a surface acoustic wave filter, and the insertion loss is measured from the transmission band near 1.5 GHz. The results are summarized in Table 1.

Further, 100 points of Al wires having a wire diameter of 25 μm were bonded to the pad electrode using a wedge bonder, and the number of peeling of the pad electrode was measured, and the bonding failure rate was expressed as a percentage. The results are summarized in Table 1.

[0062]

[Table 1]

[0063]

EFFECTS OF THE INVENTION The diamond base material and element for surface acoustic wave device according to the present invention use Al containing a metal added to the electrode material to improve the adhesion with the diamond film.
Moreover, the addition amount is controlled so as not to impair the device characteristics.

Therefore, the peeling at the time of wire bonding processing in the electrode portion is controlled, and it becomes possible to mount it on the package.

[0065]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hiroyuki Kitabayashi 1-1-1 Kunyo Kita, Itami City, Hyogo Prefecture Sumitomo Electric Industries, Ltd. Itami Works (72) Shinichi Shikada 1-1 Kunyo Kita, Itami City, Hyogo Prefecture No. 1 Itami Works, Sumitomo Electric Industries, Ltd.

Claims (10)

[Claims] 1. A surface acoustic wave device substrate having at least a diamond layer and an Al electrode portion, wherein the Al electrode portion formed on the diamond layer is made of Si, Sc, T.
A surface acoustic wave element formed of Al containing 0.1 to 5.0% by weight of at least one element of i, Cr, Mn, Ni, Nb, Mo, Pd, Ta and W. Diamond base material. 2. A surface acoustic wave device substrate having at least a diamond layer and an Al electrode portion, wherein the Al electrode portion formed on the diamond layer is Si, Sc, T.
0.1 to 5.0 wt% of at least one element of i, Cr, Mn, Ni, Nb, Mo, Pd, Ta and W, and 0.1 to 5.0 wt% of Cu. A diamond substrate for a surface acoustic wave device, which is formed of Al containing Al. 3. A surface acoustic wave device substrate having at least a diamond layer and an Al electrode portion, wherein the Al electrode portion formed on the diamond layer is Si, Ti, C.
0.1 to 5.0% by weight of at least one element out of r, Mn, Ni, Nb, Mo, Pd, Ta and W,
A diamond base material for a surface acoustic wave device, which is formed of Al containing 0.1 to 5.0% by weight of Sc. 4. The diamond base material for a surface acoustic wave device according to claim 1, wherein the diamond layer is a vapor-phase synthetic diamond. 5. A surface acoustic wave device having at least a diamond layer, a piezoelectric layer, and an exciting Al electrode portion, wherein the Al electrode portion formed on the diamond layer is S.
i, Sc, Ti, Cr, Mn, Ni, Nb, Mo, P
At least one element selected from d, Ta, and W is 0.
A surface acoustic wave device formed of Al containing 1 to 5.0% by weight. 6. A surface acoustic wave device having at least a diamond layer, a piezoelectric layer, and an exciting Al electrode portion, wherein the Al electrode portion formed on the diamond layer is S.
i, Sc, Ti, Cr, Mn, Ni, Nb, Mo, P
At least one element selected from d, Ta, and W is 0.
A surface acoustic wave device formed of Al containing 1 to 5.0 wt% and Cu of 0.1 to 5.0 wt%. 7. A surface acoustic wave device having at least a diamond layer, a piezoelectric layer, and an excitation Al electrode portion, wherein the Al electrode portion formed on the diamond layer is S.
i, Ti, Cr, Mn, Ni, Nb, Mo, Pd, T
at least one element of a and W is 0.1 to 0.1
A surface acoustic wave device formed of Al containing 5.0% by weight and 0.1 to 5.0% by weight of Sc. 8. The surface acoustic wave device according to claim 5, wherein the diamond layer is a vapor phase synthetic diamond provided on a Si substrate. 9. The piezoelectric material is ZnO or Li, N
The surface acoustic wave device according to claim 8, wherein the surface acoustic wave device is an insulating ZnO containing at least one kind of element among a, K, Rb, Mn, and Cu. 10. The surface acoustic wave device according to claim 8, wherein the piezoelectric body is LiNbO ₃ .