Electrical and piezoresistive characterization of boron-doped LPCVD polycrystalline silicon under rapid thermal annealing

Rapid thermal annealing (RTA) has been performed on boron-implanted LPCVD polysilicon films for doses ranging from 2 × 10 14 to 4 × 10 15 cm −2. We have investigated the piezoresistance through gauge-factor measurements in the scope of pressure-sensor applications and the electrical properties using Hall techniques. RTA has been carried out at 1100 °C for 20, 40 and 60 s, respectively. Gauge factors and electrical parameters deduced from Hall-effect measurements (resistivity, mobility, carrier density) are reported. We observe a reduction of the resistivity for longer RTA treatments, which is due to an enhancement 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 implantation dose. Finally, thermal budgets with shorter duration (1100 °C, 5 s) or lower temperature (1050 °C, 20 s) do not lead to uniform boron concentration throughout the film thickness.