JPH0528765Y2 - - Google Patents

Description

[Detailed explanation of the idea] [Industrial application field] The present invention relates to an electrode for a semiconductor device.

[Summary of the invention] The invention solves the problems in bonding by overlapping layers of Al and Cu on the main surface of a semiconductor device electrode to which Au wires are bonded.

[Prior Art] In a semiconductor device having an electrode and a thin metal wire bonded to the electrode, generally the electrode is made of Al, Al-Si, Al-Si-Cu, the thin metal wire is made of Au,
Al, Cu, etc. are used. Among these,
As mass-produced products, electrodes include Al, Al-Si, Al-Si-
Most of them use Cu and Au for the thin metal wire. Au wire has excellent electrical conductivity, processability, and oxidation/corrosion resistance, while Al electrode has the characteristics of making ohmic contact with Si and having good vapor deposition and etching properties.

[Problems to be solved by the invention] However, in this case, as mutual diffusion of Au and Al progresses at the junction between the Au wire and the Al electrode, various intermetallic compounds are formed as shown in Figure 2. be done. That is, in FIG. 2, an Au wire is normally bonded onto an electrode consisting of a Si layer 1, a SiO ₂ layer 2, and an Al layer 3, but Au ₄ Al
4. Intermetallic compounds such as Au ₅ Al ₂ 5, voids 6, and Au ₂ Al 7 are formed. These intermetallic compounds of Au and Al have a crystal structure different from that of the component elements Au and Al, and the lattice constant is 50% or more for intermetallic compounds.
It has increased by 70%, and it seems that the joint is under considerable stress. Since intermetallic compounds are hard and brittle, under the above-mentioned stress conditions, they are subjected to thermal cycles, causing mechanical cracks to occur, resulting in a reduction in bonding strength. Furthermore, since the rate of interdiffusion between Au and Al is fast, the Kirkendall effect occurs due to the difference in diffusion rate, and the resulting voids also cause a decrease in bonding strength.

The purpose of the present invention is to provide an electrode for a semiconductor device that solves problems at the junction between an Au wire and an Al electrode and improves bonding reliability.

[Means for solving the problem] In order to achieve this purpose, the present invention has a feature in that a layer made of Cu is placed on a layer made of Al to form the main surface. .

[Function] In this invention, a layer made of Cu is placed at the junction with the Au wire, so the rate of interdiffusion between Cu and Au and Cu and Al is slower than in the conventional case of Au and Al, and the junction Since there is no large growth of the diffusion layer even after subsequent thermal history, the reliability of the bonding part is improved.

[Example] Figure 1 shows the structure of an example of an electrode of a semiconductor device according to the present invention, in which a Si layer 1, a SiO ₂ layer 2,
In a conventional electrode consisting of an Al layer 3, a layer 9 of Cu or Cu with P added is further disposed on the Al layer 3 to form a main surface, and Au wires 8 are placed on top of the layer 9.
is bonded. When layer 9 is pure Cu,
The bonding atmosphere is filled with an inert gas or reducing gas to prevent Cu from oxidizing.

Furthermore, when P is added to pure Cu, the oxide film is easily peeled off even if the Cu is oxidized, so the oxide film is successfully peeled off by the impact during bonding, making bonding possible. The same bonding method as before is used. In addition,
By adding P to Cu, existing equipment can be used.

[Effects of the invention] As mentioned above, according to the invention, Au wire and
Problems at the joints of Al electrodes are resolved. In other words, the interdiffusion rate of Cu and Au and Cu and Al is about 1/70 slower than that of Au and Al, and there is no significant growth of the diffusion layer even after the thermal history after bonding. The reliability of the bonding part is improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of an electrode of a semiconductor device according to the present invention, and FIG. 2 is a block diagram of an electrode of a conventional semiconductor device. 1...Si, 2...SiO ₂ , 3...Al, 8...
Au, 9...Cu.

Claims (1)

[Scope of utility model registration request] 1. An electrode for a semiconductor device comprising an Au wire bonded onto a main surface of the semiconductor device, the main surface being formed by disposing a layer made of Cu on a layer made of Al.