Breakdown properties of metal/NIDOS SiO_2/silicion structures

摘要

NIDOS/SiO_2/silicon structures have been annealed in a nitrogen (N_2) ambient and X-ray photoelectron spectoscopy (XPS) characterization has been performed in order to definitively demonstrate the nitrogen atoms out-diffusion from the nitrogen doped silicon (NIDOS) film to wards the buried oxide layer.The nitridation of the SiO_2 layer is related to the competition between nitrogen atoms out-diffusion phenomena on one side into the underlying oxide layer and on the other side into an oxynitride layer grown during annealing. In order to analyse and optimize the corresponding MIS process, different structures such as metal/SiO_2/silicon, metal (NH_3-'nitrided')SiO_2/silicon, metal/(N_2O-nitrided)SiO_2/silicon, metal/poly-Si*/SiO_2/silicon (*indicates deposited from disilane Si_2H_6) and metal/NIDOS/SiO_2/silicon have been ralized and compared by capacitance-voltage, currentvoltage and ageing under constant current injection experimetns. The optimization of the NIDOS-nitridation process gives the highest charge-to-breakdown for the lowest nitridation level or even for no intentional nitridation. The dielectric breakdown improvement should therefore not be related to the nitridation phenomena alone but also to the intrinsic properties of the polysilicon layer itself.