Fabrication and characterization of thin film novel materials for microdevices and microsystems

Aluminium and aluminium alloys have been widely used as the interconnection materials to link transistors. Its application in ultra-large scale integration (ULSI) circuits is endorsed because the physical and chemical properties of aluminium are compatible with ULSI processing: Aluminium forms a thin protective oxide film, which withstands various thermal processes; it has relatively low electrical resistivity, and it is an inexpensive material. However, due to the downscaling of chips, the density of transistor increases, interconnect dimensions are decreased and the number of metal levels is raised. The shrinkage in cross-section leads to higher line resistance (R). Furthermore, their small pitch results in higher line-to-line capacitance (c). For 0.25 pm or beyond, the delay caused by A1 interconnect dominates the total delay in devices. The advantages of Cu relative to AI(Cu) for chip wiring, which include lower resistance, higher allowed current density, and increased scalability, have long been recognized. These benefits in turn have enabled the scaling of pitch and thickness. Only Cu will provide low RC characteristic capable of producing wiring speed equivalent to transistor speed