EVALUATION OF ATOMIC LAYER DEPOSITED NBN AND NBSIN AS METAL GATE MATERIALS

摘要

Nb(Si)N films deposited by thermal atomic layer deposition (ALD) have been investigated as potential gate electrode materials in advanced CMOS devices. The NbN films were deposited at 400° C using NbCl_5 and NH_3 as precursors. For NbSiN, SiCl_4 was added as a precursor, yielding an average silicon content of 3 at% [1]. The work function of these films was determined by high-frequency capacitance voltage measurements on two thickness series, one of thermal oxides (6.5 to 20nm) and one of ALD HfO_2 (2 to 6nm) followed by an O_2 post deposition anneal (PDA). It was found that NbN has a work function of ~4.7 eV on SiO_2 and —4.9eV on HfO_2. However, thermal stability is limited to ~950° C. The thermal stability on SiO_2 is increased by incorporation of silicon into the NbN. NbSiN has a work function ~4.7 eV on SiO_2 and ~4.8eV on HfO_2.