Copper interconnect

In semiconductor technology, copper interconnects are interconnects made of copper. They are used in silicon integrated circuits (ICs) to reduce propagation delays and power consumption. Since copper is a better conductor than aluminium, ICs using copper for their interconnects can have interconnects with narrower dimensions, and use less energy to pass electricity through them. Together, these effects lead to ICs with better performance. They were first introduced by IBM, with assistance from Motorola, in 1997. The transition from aluminium to copper required significant developments in fabrication techniques, including radically different methods for patterning the metal as well as the introduction of barrier metal layers to isolate the silicon from potentially damaging copper atoms. Although the methods of superconformal copper electrodepostion were known since late 1960, their application at the (sub)micron via scale (e.g. in microchips) started only in 1988-1995 (see figure). By year 2002 it became a mature technology, and research and development efforts in this field started to decline. Patterning Although some form of volatile copper compound has been known to exist since 1947, with more discovered as the century progressed, none were in industrial use, so copper could not be patterned by the previous techniques of photoresist masking and plasma etching that had been used with great success with aluminium. The inability to plasma etch copper called for a drastic rethinking of the metal patterning process and the result of this rethinking was a process referred to as an additive patterning, also known as a "Damascene" or "dual-Damascene" process by analogy to a traditional technique of metal inlaying.