JPS6410097B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a semiconductor device having multilayer wiring formed on a semiconductor wafer including a device, and in particular to a method for manufacturing a metal wiring made of aluminum (Al) or an aluminum-based alloy. The present invention relates to a method for manufacturing metal interconnects for semiconductor devices that prevents shorts between interconnects due to the occurrence of whiskers.

In general, in semiconductor devices such as LSIs, increasing density is necessary to improve integration and reduce power consumption, and while reducing wiring spacing is required, multilayer wiring is also known as an effective method. ing.
Conventionally, Al has been mainly used on this wiring metal, but this material has good adhesion to insulating films such as silicon oxide, provides mechanically strong wiring, and is easy to vapor-deposit and film. It is also possible to control the thickness.
This is due to the high electrical conductivity and low resistance of wiring. This Al vapor deposition method includes, for example, an Al vapor deposition method using resistance heating, an E-gun method that melts Al with an electron beam, and a sputter vapor deposition method that uses Ar sputtering. In this method, an Al wire is placed on a filament made of aluminum, and the filament is heated to melt the Al and vaporize it in a vacuum. In this method, the purity of the W and Ta filaments themselves is poorer than that of Al itself, and various impurities usually mix into the Al deposited film. In addition, the E-gun method uses
In a vacuum by melting Al with an electron beam
Although it is used to melt Al vapor, the material of the crucible is generally not of high purity. in this way,
In the vapor deposition method using resistance heating or the E-gun method, whiskers were not generated because the presence of impurities in the Al film was large.

By the way, as mentioned above, in order to avoid adverse effects on semiconductor devices due to impurities contained in the filament itself or impurities contained in the crucible, high-purity Al films formed by sputter deposition using sputtering of Ar, etc. have recently become available. has come to be used for wiring. this
Al films have less of an effect on semiconductor devices, but as the purity of Al films has increased, the generation of whiskers has become a new problem. These whiskers are more likely to occur due to the heat cycle of compression and expansion that is repeated during wiring processing and subsequent wafer processing, and as metals, not just Al, become highly purified, whiskers become more likely to occur. It is well known that this is more likely to occur. Therefore, as the degree of integration increases and the wiring spacing is reduced, resulting in high-density wiring, such as in semiconductor devices such as LSIs, whiskers that occur in metal wiring can have a serious impact on semiconductor devices. Become. For example, if high-purity Al is used for multilayer wiring of LSI, and whiskers of 2 to 10 μm are generated during processing, the Al wiring spacing is 2 μm.
~3μm, insulation film between first layer and second layer wiring is 1~2μm
In view of this, there was a problem in that the generation of whiskers causes shortening between Al layers, which not only lowers the yield of devices but also lowers reliability.

The present invention has been made in order to eliminate the above-mentioned conventional drawbacks, and its purpose is to manufacture metal interconnects in semiconductor devices that prevent shorts between interconnects due to the generation of whiskers during processing of metal interconnects such as Al. The purpose is to provide a method.

To achieve this objective, the present invention injects phosphorus (P ⁺ ), arsenic (As ⁺ ), argon (Ar + ), and antimony (Sb ⁺ ) into metal interconnects such as Al formed on semiconductor wafers containing ^devices. ) and other impurities, i.e. ion species with a mass of 30 or more, are ion-implanted to a depth of approximately 800 to 2000 Å from the surface of the metal wiring to remove whiskers generated in the metal wiring during processing. It is. In this case, ion implantation of impurities can be performed relatively easily using normal techniques, and among these impurities, P ⁺ , As ⁺ , and Sb ⁺ are ion species used to form PN junctions in semiconductors. , Ar ⁺ is also an ionic species used for gettering.

Examples of the present invention will be described below.

FIG. 1 is a schematic explanatory diagram showing one embodiment of the present invention, in which 10 is a Si wafer including a device having a PN junction, 11 is an SiO ₂ film formed on the Si wafer 10, and 12 is an Si wafer including a device having a PN junction. A high-purity Al film as a metal wiring is formed on this SiO ₂ film 11 by sputter deposition and has a film thickness of about 7000 Å.
In this example, impurities such as P ⁺ , Ar ⁺ , and As ⁺ are ion-implanted into the Al film 12 within a range of approximately 800 to 2000 Å from the surface of the Al film 12.
Whiskers generated on the Al film 12 can be removed.

FIG. 2 shows an example of experimental results for confirming the effects of the above-mentioned embodiment. In the present invention, the sample having the structure shown in FIG. By generating whiskers in the film and investigating the correspondence between the whisker generation density and the depth of impurities such as As ⁺ and P ⁺ ion-implanted into the Al film, we were able to obtain an impurity depth that extremely effectively prevents whiskers. It is based on In other words, as shown in Fig. 2, P ⁺ , Ar ⁺ , and As ⁺ have a very similar relationship, and when ions are implanted to a depth of approximately 800 to 2000 Å, which is indicated by the symbol A in Fig. 2, the generation of whiskers is eliminated. It disappears. For example, in the case of P ⁺ , whiskers were generated when ions were implanted to a depth of about 0.01 μm from the surface of the Al film 12, as indicated by the symbol B in FIG. Also, for B ⁺ , the injection energy
When ion implantation is performed under the conditions of 150 KeV and an implantation amount of 4×10 ¹⁵ cm ⁻² , B ⁺ is implanted at a position of 4500 Å from the 7000 Å thick surface of the Al film 12 as indicated by the symbol C in FIG. However, whiskers did occur in this area. From this, it can be said that in order to prevent the generation of whiskers, it is preferable to implant impurity ions into the whisker generation source at a distance of 800 to 2000 Å from the surface of the Al film 12 as indicated by the symbol A in FIG.

In addition, Ar ⁺ and Sb ⁺ are impurities other than As ⁺ and P ⁺ .
It was found that a similar effect could be obtained by ion implantation. At this time, if ions are implanted under the same conditions, in the case of H ⁺ , Al
Although the light passed far through the membrane 12, whiskers were generated in this region of code D. In Fig. 2, the horizontal axis shows impurity ions, and the vertical axis shows the projected range (R _p ) of ions implanted into the Al film for the sample in Fig. 1, and the symbols R _p and σ are The projected range and standard deviation of each impurity ion are shown.

Note that in order to maintain the resistance value of the Al film almost as it is, it is preferable to keep the impurity to about 0.5%. Moreover, it contains 800 to 2000 impurities of 0.5% or more.
Ion implantation to a depth of Å is the best condition for whisker prevention.

It cannot be easily explained that whiskers are less likely to occur by introducing these impurities into the Al film, but it is possible to introduce the whisker generation source into the Al film at a depth of approximately 800 to 2000 Å from the surface. It can be said that it is removed by doing so.

Conventionally, measures to prevent whiskers on Al films formed by sputter evaporation have been aimed at, for example, by using a low temperature process during wiring processing of Al films, or by reducing heat cycles. According to the example, it was confirmed that there is no problem even if heat cycles occur several times in a process at a temperature of about 180 to 500° C. after the wiring step in a wafer process generally used for semiconductor processing. This indicates that the restrictions on semiconductor processing equipment will be relaxed and the range of equipment selection will be expanded.

Although the above example shows the case of Al, this method is also effective against the generation of the same kind of whiskers that will occur when Mo, W, etc., which are promising wiring materials, are used in high purity in the future. It is easy to infer that this is the case.

Additionally, it should be noted that by implanting H ⁺ and B ⁺ , the whisker density is reduced to about half of that before ion implantation. However, the second
As shown in the figure, if the ion implantation is too deep, whiskers cannot be completely eliminated.

As explained above, according to the present invention, a metal wiring such as Al formed on a semiconductor wafer including a device has a concentration of 30 or more by mass as much as 0.5% or more with respect to the metal wiring. ⁺ ，As ⁺
approximately 800% of ionic species such as
By implanting ions to a depth of ~2000 Å, it is possible to remove whiskers that occur in metal wiring during processing, which prevents shorts between wiring and improves the quality of metal wiring without changing wiring resistance. can be obtained, and therefore,
This has the effect of improving the yield and reliability of semiconductor devices.

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram showing an embodiment of the present invention;
FIG. 2 is a diagram illustrating the relationship between whisker generation and ion implantation depth, showing an example of the experimental results of the above embodiment. 10...Si wafer, 11...SiO ₂ film, 12...
...Al film.

Claims (1)

[Claims] 1. In a method for manufacturing a semiconductor device having a high-purity metal wiring made of aluminum or the like formed on a semiconductor wafer including a device, the metal wiring has a mass of argon, phosphorus, arsenic, etc. of 30 or more. 1. A method for manufacturing a semiconductor device, comprising the step of implanting ion species to a depth of approximately 800 to 2000 Å from the surface of the metal interconnection to a depth of 0.5% or more.