Tin sources and trade in ancient times Bantu culture of Zimbabwe are known to have actively mined, smelted and traded tin between the 11th and 15th centuries AD . Tin deposits exist in many parts of South America, with minor deposits in southern Peru, Colombia, Brazil, and northwestern Argentina, and major deposits of exploitable cassiterite in northern Bolivia. These deposits were exploited as early as 1000 AD in the manufacture of tin bronze by Andean cultures, including the later Inca Empire, which considered tin bronze the "imperial alloy". In North America, the only known exploitable source of tin during ancient times is located in the Zacatecas tin
Copper interconnect is to use Cu-Ge alloy as the interconnect material so that buffer layer (e.g. TiN) is no longer needed. Epitaxial CuGe layer has been fabricated with an average resistivity of 6 ± 1 μΩ cm and work function of ~4.47 ± 0.02 eV respectively, qualifying it as a good alternative to Cu. Resistance to electromigration, the process by which a metal conductor changes shape under the influence of an electric current flowing through it and which eventually leads to the breaking of the conductor, is significantly better with copper than with aluminium. This improvement in electromigration resistance allows higher currents