JPH0624205B2 - Semiconductor device - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a semiconductor device.

[Background of the Invention]

Conventionally, Cu-added Al has been used in the electrodes and wirings of semiconductor devices to avoid the problem of electromigration, as described in US Pat. No. 3,743,894.

Al is generally used for the wiring of the semiconductor device. When this device is operated under high current and high temperature,
The l-wiring film is moved by the electric current flowing through it, causing the metal to rise in some areas and form voids in other areas. If this void becomes large enough, it will increase the resistance of the metal contact in the area where it occurred sufficiently to cause resistance heating and melting of the contact metal, which could lead to premature accidents of this equipment. .

According to said U.S. patent, Al is mixed with 1-10 wt% Cu to avoid this electromigration problem. Therefore, a fine grain structure of Cu Al ₂ grains is formed, and these are present at the Al grain boundaries and the grain boundary triple points, and it is possible to prevent atomic migration of Al and prolong the life of the device against electromigration.

In the present invention, the wiring film is formed by using Cu having a resistivity lower than that of Al, and the current density can be made larger than that of Al. Further, since the melting point of Cu is 400 ° C. or more higher than that of Al, it is possible to prevent an early accident of the device due to electromigration. By thus forming the wiring with Cu, the width of the wiring film can be reduced and the packaging density of the semiconductor substrate can be increased. At the same time, it is possible to prevent early destruction of the device due to electromigration.

[Object of the Invention]

An object of the present invention is to provide a highly reliable semiconductor element by using Cu having excellent electromigration resistance in place of the conventional semiconductor Al wiring film.

[Outline of Invention]

Conventionally, pure Al or Si-containing Al has been used for electrodes and wiring of semiconductor devices. However, pure Al, Si containing Si
Has a low electromigration resistance, and when a current having a high current density is applied, the contact resistance between the electrode and the semiconductor substrate increases. Alternatively, there is a defect that the wiring is broken due to atom movement.

Although Cu-containing Al wiring has electromigration resistance, the addition of Cu increases the specific resistance of the Al wiring, so that when a current is applied, the temperature of the element rises remarkably, causing a malfunction of the element. Becomes Also Cu containing Al
Since Cu is dispersed in the Al base in the wiring, there is a drawback that Al atoms and Cu atoms act as a local battery during etching and the pattern accuracy of the Al wiring deteriorates. In particular, for Cu-containing Al wiring having a wiring width of 1 μm or less in an element having a high integration density, a high level of processing technology is required to ensure patterning accuracy.

In order to eliminate these drawbacks, the present invention uses pure Al or Al containing Si and Cu for the wiring part through which a current flows, in order to eliminate these drawbacks. It is to realize highly stable electrodes and wirings of semiconductor devices that require high integration and high precision. Further, by using a Cu wire as a bonding wire for connecting the lead frame and the element, the Cu on the semiconductor substrate is
There is an advantage that the bonding pad portion of the wiring film and the Cu wire can be directly bonded. Furthermore, in this case, by using a copper lead frame, the wiring film on the semiconductor substrate, the bonding wires, and the lead frame are all made of copper, providing a semiconductor device with excellent moisture resistance reliability and stability. can do.

Further, the crystal grain of the Cu wiring film is smaller than the wiring width and the crystallinity is preferentially oriented in the [111] or [100] direction with respect to the semiconductor substrate, whereby the electromigration resistance can be further enhanced.

Next, the reason will be described. The electrical resistivity of Si-containing Al is 3.1 μΩcm, while that of Cu is as small as 1.5 μΩcm, and the melting point of Si-containing Al is 660 ° C. or less, whereas that of Cu is as high as 1083 ° C. When the current is applied at the same current density, Cu has a smaller temperature rise and a smaller degree of softening. Furthermore, the stacking fault energy, which indicates the number of sloping faces of the crystal, is small for Cu in the (111) plane (40 erg / cm
₂ ), large for Al (200 erg / cm ₂ ). This means that the surface density of Al is several times higher than that of Cu.
Means that electromigration tends to occur when a current is applied.

On the other hand, not only the Cu wire is bonded to the Cu wiring but also the conventional Au wire or Al wire is used for bonding, so that the bonding pad portion of the Cu wiring film on the semiconductor substrate is pure Al or has excellent bonding stability. An Al layer to which at least one of Ni, Pd, and Pt is added may be deposited. By using this method, it is possible to provide a semiconductor device having high reliability equivalent to that of bonding with a Cu wire by utilizing conventional equipment.

By subjecting the semiconductor device thus manufactured to the ceramics molding, the reliability of the product can be secured even in a bad environment. Further, instead of the ceramic mold, resin molding mainly composed of epoxy resin can be performed to protect the internal semiconductor substrate from the external environment.

Example of Invention

 Hereinafter, the present invention will be described in detail with reference to examples.

FIG. 1 is a sectional view showing the structure of an embodiment of the present invention.
In the figure, 1 is a semiconductor substrate (Si substrate, Ga-As substrate), 2 is a diffusion layer in which impurities (for example, P, As, B, Al, etc.) are diffused, 3 is a windowed insulator (for example, a thickness of 0). 1 to 0.5 μm of SiO ₂ film or PSG film), 4 is formed of pure Al or an Al layer containing Si (0.1 to 0.5 μm in thickness by vapor deposition, sputtering, CVD, etc., and photo etching) After patterning by 350 ~ 5
Stabilize by heat treatment at 50 ° C. for 5 to 60 minutes. ), And is in contact with the diffusion layer 2 through the contact 5. 6 is a Cu layer having an electric resistivity which is half that of Al (for example, a thickness of 0.5 is formed by vapor deposition, sputtering, CVD, etc.).
After depositing ˜2 μm and patterning, heat treatment at 250 to 550 ° C. is applied for 5 to 60 minutes to stabilize. ), And is in contact with the electrode 4. Reference numeral 7 is a protective film (for example, 0.5 to 2.0 μm thick SiO ₂ film or PSG film) for protecting the surface of the element, and the bonding pad portion 8 is opened. Numeral 9 is a Cu bonding wire which is bonded to the pad portion 8 (by thermocompression bonding or ultrasonic bonding).
To be done.

With this structure, as described below, the electromigration resistance is higher than in the case of using pure Al or Si-containing Al for the wiring portion, and the conventional Al wiring film,
Moisture-resistant reliability is also improved compared to resin-molded semiconductor products composed of Au bonding wires.

FIG. 2 is a graph for explaining the effect of the present invention,
When using conventional Si-containing Al as the wiring material,
3 shows a change with time in resistance value in a high-temperature current test when using the Cu wiring of the present invention. As is clear from the figure, the Cu wiring is more stable than Al containing Si.

The reason for this is that the electrical resistivity of Al containing Si is 3.1 μΩcm.
On the other hand, that of Cu is as small as 1.5 μΩcm, and Si
While the melting point of Al containing Al is 660 ° C or lower, Cu
Since it is as high as 1083 ℃, it is C at the same current density.
This is because u has a smaller temperature rise and a smaller degree of softening.

Fig. 3 shows the combination of Cu wiring and Cu bonding wire when resin-molded, the conventional Si-containing Al wiring, A
u The results of an accelerated life test (2 atmospheric pressure saturated steam test) in the case of combining bonding wires are shown. As is clear from the figure, the combination of Cu wiring and Cu wire is superior in moisture resistance reliability and the life is 2 to 2.5 times as long as the conventional method.

The reason for this is that Al and Au are bonded in the conventional method, and when water enters the bonding part, a local battery is formed and electrically base Al is melted, whereas in the present invention, It is considered that due to the combination of Cu wiring and Cu wire, a local battery is not formed and corrosion resistance is improved.

In summary, according to the present invention, it is considered that the reliability for electromigration and the moisture resistance reliability can be simultaneously satisfied.

FIG. 4 is a sectional view showing the structure of another embodiment of the present invention. In the figure, the same reference numerals in FIG. 1 described above indicate the same or equivalent portions. This embodiment is intermediate in Ni of the first bonding of Cu wiring in the embodiment of Figure Patsu head portion 8 and the Au or Al or Cu wires 11, Pd, and at least one or more elements of P _t 0.0
Al layer 10 containing 1 to 3% (for example, thickness of 0.1 to 1.0 μm)
m) is deposited. It is known that the Al layer 10 has corrosion resistance, and it serves to prevent the stability of bonding between the bonding wire and the Cu wiring film from being impaired and to have moisture resistance reliability.

As described above, according to the present invention, a wiring having high electromigration resistance and excellent moisture resistance reliability can be obtained.

Further, by providing an Al layer having corrosion resistance on the bonding pad, any of Au, Al and Cu wires can be bonded easily, and the stability of bonding is maintained even when heat treatment is applied after the electrode / wiring formation. ,
A highly reliable semiconductor element can be manufactured when the ceramics molding or the resin molding is performed.

Next, the effect of the present invention will be described with respect to the structure of the Cu wiring film. FIG. 5 shows the change with time in the resistance value in the high temperature current test when the substrate temperature was changed and the crystal grain size was made smaller than the wiring width (1 μm) when the Cu wiring film was formed. As is clear from the figure, the smaller the crystal, the higher the stability, and the larger the crystal grain is, the shorter the life.

The reason for this is thought to be that the smaller the crystal grains, the more uniformly grain boundary diffusion occurs, and when the wiring width and the size of the crystal grains are about the same, the wiring breaks from the grain boundaries due to the influence of grain boundary diffusion.

FIG. 6 shows the crystallinity of the Cu wiring film with respect to the semiconductor substrate [1.
11] or the [100] direction is preferentially oriented (for example, it is formed by a sputtering method at a substrate temperature of 150 ° C. or higher) and the crystal orientation is absent. . As is apparent from the figure, stability is high in the case of preferential orientation in the [111] or [100] direction.

The reason for this is that since Cu is a face-centered cubic lattice, the stagnation system with the maximum shear stress during stagnation deformation is the {111} plane. At that time, crystals are [111] or [10] against the semiconductor substrate.
0] direction, the dislocations moving on the {111} plane are deposited toward the barrier of immovable dislocations and the movement of dislocations is hindered to strengthen the Cu wiring film. It is thought to be because.

As described above, by using the Cu wiring film having the structure according to the present invention, a highly reliable semiconductor element having high electromigration resistance can be manufactured.

〔The invention's effect〕

According to the present invention, a wiring film for a semiconductor having excellent corrosion resistance and electromigration resistance can be obtained. As a result, it can be applied to a high density and fine wiring pattern of a semiconductor element of resin mold or ceramics mold, and the reliability of a semiconductor device can be improved.

[Brief description of drawings]

1 and 4 are sectional views showing the structure of an embodiment of the present invention, and FIGS. 2, 5 and 6 are diagrams showing electromigration resistance by the effect of the present invention,
FIG. 3 is a graph showing the effect of moisture resistance according to the present invention. 1 ... Semiconductor substrate, 2 ... Diffusion layer, 3 ... Insulator, 6 ...
… Cu layer, 7 …… Protective film, 8 …… Bonding pad,
9 ... Cu wire, 11 ... Bonding wire.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-59-43570 (JP, A) JP-A-53-116089 (JP, A) JP-A-59-143320 (JP, A) Actual development Sho-58- 18345 (JP, U)

Claims (4)

[Claims] 1. A semiconductor substrate having a diffusion layer inside, an insulating layer formed on the semiconductor substrate, and a wiring layer made of Cu formed on the insulating layer, the wiring layer comprising: A semiconductor device, wherein the diffusion layer is contacted via an electrode made of pure Al or Si-containing Al, and a Cu bonding wire is bonded to the bonding pad portion of the wiring layer by wire bonding. 2. A semiconductor substrate having a diffusion layer inside, an insulating layer formed on the semiconductor substrate, and a wiring layer made of Cu formed on the insulating layer, wherein the wiring layer comprises: The diffusion layer is contacted via an electrode made of pure Al or Si-containing Al, and the bonding pad portion of the wiring layer has a pure Al layer or at least one element selected from Ni, Pd, and Pt. And a bonding wire made of Au, Al, or Cu is bonded to the layer by wire bonding. 3. A semiconductor device according to claim 1 or 2, wherein the size of the crystal grains of Cu forming the wiring layer is smaller than the wiring width of the wiring layer. . 4. Claims 1, 2, or 3
2. The semiconductor device according to the item 1, wherein the crystallinity of Cu forming the wiring layer is preferentially oriented in the [111] or [100] direction with respect to the semiconductor substrate.