Efficiency of TiN diffusion barrier between Al and Si prepared by reactive evaporation and rapid thermal annealing

TiN layers prepared by reactive evaporation and rapid thermal annealing were tested as diffusion barrier between Al and Si. First, Rutherford backscattering spectroscopy (RBS) analysis of Al/Ti(N)/Ti/Si and Al/Ti(N)/Si multilayer structures showed that Si does not diffuse out up to a sintering temperature of 550 degrees C. However, as the temperature increases beyond 450 degrees C, Al starts to react with TiN. This reaction leaves less than half the TiN original thickness after a 30 min anneal at 550 degrees C. The RBS results indicate that TiN, crystallized at a temperature around 850 degrees C, forms a good barrier between Al and Si. Electrical measurements on various microelectronic devices were performed to verify this. Annealing of Ti(N) at 900 degrees C leads to a breakdown of p-MOS (metal-oxide-semiconductor) devices while n-MOS devices still work properly. Annealing at 800 degrees C gives good results on both MOS types except that the contact resistance of a p-type resistor is higher than desired. The electrical circuit failure is mainly due to dopant loss from the active area of the device into the titanium silicide which forms during the rapid thermal annealing at 800 or 900 degrees C of the deposited Ti(N) layers. (C) 1996 American Institute of Physics.