ELECTRICAL AND PIEZORESISTIVE CHARACTERIZATION OF BORON-DOPED LPCVD POLYCRYSTALLINE SILICON UNDER RAPID THERMAL ANNEALING

Rapid thermal annealing (RTA) has been performed on boron-implanted LP CVD polysilicon films for doses ranging from 2 x 10(14) to 4 x 10(15) cm(-2). We have investigated thr piezoresistance through gauge-factor measurements in the scope of pressure-sensor applications and the elec trical properties using Hall techniques. RTA has been carried out at 1 100 degrees C for 20, 40 and 60 s, respectively. Gauge factors and ele ctrical parameters deduced from Hall-effect measurements (resistivity, mobility, carrier density) are reported. We observe a reduction of th e resistivity for longer RTA treatments, which is due to an enhancemen t of the mobility. Moreover, the carrier concentration does not depend on the heat-treatment duration. The gauge factor does not show a very strong dependence on the annealing duration but rather on the implant ation dose. Finally, thermal budgets with shorter duration (1100 degre es C, 5 s) or lower temperature (1050 degrees C, 20 s) do not lead to uniform boron concentration throughout the film thickness.