The semiconductor industry is continuing its quest to create ever more powerful CPU and memory chips. These efforts are focused principally in two areas. On one hand, the speed of individual devices is increased through the continual reduction of the minimum size of device features. Along with this goes a corresponding increase in device density on the chip. On the other hand, in order to take advantage of increased device speeds, one needs to connect individual devices into circuits using increasingly complex interconnect schemes. These now involve multilayer structures made up of several levels of metal wiring separated by an interlayer dielectric (ILD). Efforts in both of these areas are supported by more and more sophisticated device and circuit design.
The exact nature of the trade-off between individual device and interconnect performance depends on details of the circuit architecture. However, it is now generally recognized that the overall circuit performance is going to be dominated by the efficiency with which devices are connected rather than by the speed of the individual devices. From the materials point of view, a better interconnect efficiency may be achieved with various new materials combinations for the metal and the interlayer dielectric (ILD). It is now becoming apparent that a major component of improved interconnect performance will consist in replacing aluminum, the previous metal of choice, with copper.
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