Conduit Diffusion of Dopants in Tungsten Silicide Layers

Novel test diode structures have been manufactured to characterise dopant diffusion in tungsten silicide layers. Bipolar diode action is demonstrated experimentally for anneal schedules of 30 minutes at 900°C, indicating long- range diffusion of phosphorus (~ 38 μm). The work function of the silicide was found to be 4.8 eV. SIMS analysis shows dopant redistribution is effected by the segregation to the silicide/oxide interface. The concept of conduit diffusion has been demonstrated experimentally for application in advanced bipolar transistor technology.