JPH0691125B2 - Semiconductor device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, and more particularly, it enables wire bonding of a semiconductor element and an electrode pad with a Cu wire to prevent a purple break of a wire bonded electrode pad portion. It has improved reliability.

2. Description of the Related Art Generally, in a semiconductor device, for example, a semiconductor integrated circuit (IC),
Aluminum films are used for the emitter electrode, base electrode, collector electrode, gate electrode, source electrode, drain electrode, and other electrodes of the transistor element, and the electrode pad for wire bonding is formed of an aluminum alloy film. Further, as a bonding wire for connecting the electrode pad and the lead terminal of the semiconductor container (lead frame), an Au wire having a diameter of 20 to 30 μm is often used. Although other Al wires are also used as the bonding wire, the Au wire is generally used because the wiring work (nail head bonding) is easy.

Problems to be Solved by the Invention In a typical semiconductor device, as shown in FIG. 3, after wire bonding a metal wire (3) to an electrode pad portion of a wiring made of an aluminum film (2) on a semiconductor element (1),
Molded with resin (4), but metal wire (3)
The wire bonding using Au wire for the wire not only makes the wiring cost high, but also causes a purple break (5) between the aluminum film (2) and the metal wire (3) due to long-term use, which eventually leads to wiring. Is known to lead to.

In the purple break, Al and Au react with each other to generate AuAl ₂ (purple compound), which is destroyed when the contact resistance increases, and when the wire breaks, the entire electrode pad turns into purple. Also, in resin mold encapsulation, the joint between the electrode pad and the Au wire is inevitably exposed to the outside air containing water, which is corroded, which causes severe corrosion due to the addition of the electrolytic corrosion effect. It's a problem.

Means for Solving the Problems The present invention has been studied in view of the above problems, and instead of Au wire or Al wire, wire bonding with an inexpensive Cu wire is enabled, and a purple break of an electrode pad portion is prevented to improve reliability. We have developed a semiconductor device with improved performance.In a device in which a metal wire is wire-bonded to the electrode pad part of the wiring made of an aluminum film on a semiconductor element and sealed, a metal silicide layer is formed on the aluminum film of the electrode pad part. It is characterized in that it is coated with Cu or a Cu alloy through it, and that a Cu wire is used as a metal wire to wire-bond it.

That is, according to the present invention, as shown in FIG. 1, a Cu or Cu alloy layer (7) is provided on an electrode pad portion of a wiring formed of an aluminum film (2) on a semiconductor element (1) via a metal silicide layer (6).
And a Cu wire as a metal wire (3) is wire-bonded to this and is mold-sealed with a resin (4) or the like.

As metal silicide, NbSi, TiSi, ZrSi, NiSi,
CoSi, FeSi, PdSi, VSi, PtSi, MoSi, WSi and the like are used, and the thickness thereof is preferably 500 Å or more, practically 500 to 2000 Å, and is formed by sputtering or vapor deposition. Further, as the Cu or Cu alloy layer, in addition to pure Cu, Cu-
Ag, Cu-Au, Cu-Mg, Cu-P, Cu-B, Cu-Al, Cu-S
n, Cu-Ti, Cu-Zn, etc. are used, and the thickness is 1000Å
As mentioned above, it is desirable to set it to 1000 to 10,000Å for practical use.
It is formed by sputtering or vapor deposition.

If it is desired to improve the bondability between the aluminum film and the metal silicide layer and between the metal silicide layer and the Cu or Cu alloy layer, an intermediate layer, such as Cr or Ti, having a thickness of 1000 Å or less is formed between them. For example, as shown in FIG. 2, the metal silicide layer (6) and Cu or Cu deposited on the electrode pad portion of the wiring made of the aluminum film (2) on the semiconductor element (1)
By providing the intermediate layer (8) between the alloy layer (7) and the alloy layer (7), the bondability between the two can be improved.

By forming a Cu or Cu alloy layer on the aluminum film of the working electrode pad via a medal silicide layer, an inexpensive Cu wire can be used as a bonding wire. Cu wire is superior in strength and conductivity to Au wire and Al wire, and it becomes a bond between Cu wire and Cu pad, so that various problems in corrosion resistance can be eliminated.

Particularly, in the case of a Cu-based lead frame, the same material (monometal) is achieved, and electrolytic corrosion during use of the semiconductor device can be reliably prevented. Metal silicide is a high melting point corrosion resistant substance and a good conductor of electricity, effectively acts as a barrier between the aluminum film and Cu or Cu alloy layer to prevent the diffusion of both, and the wire bonding property of Cu wire. To improve.

Example As shown in FIG. 1, an Al film, a metal silicide layer, and a Cu or Cu alloy layer were sequentially deposited on a semiconductor element by sputtering to form electrode pads shown in Table 1. This element
Die-bonded on the tab of the lead frame made of Cu-2% Sn-0.15% Cr alloy, and the electrode pad had a purity of 99.999 with a diameter of 25 μm.
% Of pure Cu wire was wire-bonded and then mold-sealed with epoxy resin to fabricate a semiconductor device. This device was alternately immersed in a eutectic solder bath at 250 ° C and cold water 5 times, and then moistened at 121 ° C pre-tacker (2 atm).
For 1000 hours (A treatment) and at a temperature of 120 ° C for 5 hours
After being held for 000 hours, the failure rate was examined for the same pre-cushion cuter treatment (B treatment). The results are also shown in Table 1.

As is clear from Table 1, the failure rates of the present invention devices Nos. 1 to 5 are all significantly improved, which is far superior to the conventional device in which the Au wire is wire-bonded to the electrode pad made of an aluminum film. There is. On the other hand, it is understood that the comparative device No. 6 in which the metal silicide layer is not formed and the comparative device No. 7 in which the Cu wire is wire bonded to the electrode pad made of the aluminum film have a high failure rate. The reason why the failure rate of the device of the present invention is low is that the device exhibits high corrosion resistance even when water enters.

As described above, according to the present invention, the surface layer of the electrode pad is made of Cu or a Cu alloy, and by using an inexpensive Cu wire for the bonding wire, the deterioration of the wire bonding part is significantly reduced, and the reliability of the device is improved. It is remarkably improved and has a remarkable effect industrially.

[Brief description of drawings]

1 is a sectional view showing an example of an electrode pad portion of the device of the present invention, FIG. 2 is a sectional view showing another example of an electrode pad portion of the device of the present invention, and FIG. 3 is an example of an electrode pad portion of a conventional device. FIG. 1 ... Semiconductor element, 2 ... Aluminum film, 3 ... Bonding wire, 4 ... Resin, 5 ... Purple break 6 ... Metal silicide layer 7 ... Cu or Cu alloy layer

Claims (1)

[Claims] 1. In a device in which a metal wire is wire-bonded and sealed in an electrode pad portion of a wiring made of an aluminum film on a semiconductor element, Cu or Cu is provided on the aluminum film of the electrode pad portion via a metal silicide layer. A semiconductor device characterized in that it is coated with an alloy and is wire-bonded by using a Cu wire as a metal wire.