Electric property improvement and boron penetration suppression in metal-oxidase-Si capacitors by amorphous-Si gate electrode and two-step nitridation

The improvement of electric property;and reduction of boron penetration in metal-oxide-Si (MOS) capacitors are deafly achieved by the combination of a gate electrode deposited using amorphous Si(a-Si) and a gate oxynitride fo rmed by a two-step N2O nitridation. The charge-to-breakdown performance of MOS capacitors fabricated by this technique is excellent. The hot-electron induced interface traps and flatband voltage shifts are significantly reduc ed. This reliability improvement can be explained in terms of a mechanism b ased on an increase in compressive stress (macroscopic strain) in the oxyni tride and relaxation of SiO2/Si interfacial strain. Also this improvement c an be due to a reduction of hydrogen-related species diffused from the rate electrode, which is achieved by nitrogen pileup at the gate electrode/oxyn itride interface. Boron penetration is significantly suppressed by an a-Si gate electrode because of a larger grain size and a longer dopant diffusion path. The boron penetration is also clearly reduced by a gate oxynitride f ormed using a two-step N2O nitridation. Boron penetration reduction for thi s oxynitride can be attributed to the nitrogen incorporation into the gate electrode/oxynitride interface. This approach would be useful for the proce sses of gate electrode and gate dielectric in the deep submicron MOS transi stors. (C) 2001 American Vacuum Society.