DEGRADATION OF OXYNITRIDE GATE DIELECTRIC RELIABILITY DUE TO BORON-DIFFUSION

In this letter, we report on the impact of the suppression of boron di ffusion via nitridation of SiO2 on gate oxide integrity and device rel iability. SiO2 subjected to rapid thermal nitridation in pure nitric o xide (NO) is used to fabricate thin oxynitride gate dielectrics. Both n(+) polycrystalline silicon (polysilicon) gated n-MOS (metal-oxide se miconductor) and p(+)-polysilicon gated p-MOS devices were subjected t o anneals of different times to study the effect of dopant diffusion o n gate oxide integrity. As expected, an advanced oxynitride gate diele ctric will effectively alleviate the boron-penetration-induced flatban d voltage instability in p(+)-polysilicon gated p-MOS capacitors due t o the superior diffusion barrier properties. However, such improvement s are observed in conjunction with some degradation of the oxide relia bility due to the boron-blocking/accumulation inside the gate dielectr ic. Results show that even though the oxide quality is slightly degrad ed for NO-nitrided SiO2 with p(+)-polysilicon gates, p-MOSFETs (metal- oxide semiconductor field effect transistors) with these dielectrics s till show improved interface stability as compared to conventional SiO 2 due to the reduced boron penetration into the Si/SiO2 interface and underlying channel region. (C) 1996 American Institute of Physics.