Effects of TiN deposition on the characteristics of W/TiN/SiO2/Si metal oxide semiconductor capacitors

We report the effects of the TiN deposition technique on the generation and annihilation of interface traps and oxide trapped charges in W/TiN/SiO2 (2-6 nm)/Si,metal oxide semiconductor (MOS) system during direct metal gate process. The TiN films were prepared by reactive sputtering using the Ti target or chemical vapor deposition (CVD) using TiCl4 and NH3. Sputter-deposited TiN not only generated a high level of interface traps similar to2 x 10(12) eV(-1) cm(-2) from the bandedge to the near midgap of Si, but also introduced oxide trapped charges (Q(ot)) of similar to1 x 10(12) cm(-2). The damages annealed out for SiO2 (greater than or equal to3 nm) to the range of 2-3 x 10(11) eV(-1) cm(-2) by the post-metal anneal (PMA) at 800 degreesC in N-2 or at 450 degreesC in forming gas. The interfacial damages for ultrathin SiO2 (similar to2 nm), however, were hardly capable of relieving even after the PMA of 800 degreesC, resulting in an interface trap density (D-it) in the high 10(11) eV(-1) cm(-2) range. The D-it level created after CVD-TiN was as low as similar to3 x 10(11) eV(-1) cm(-2) with negligible Q(ot) even without PMA, and this level was further reduced to similar to1 x 10(11) eV(-1) cm(-2) after PMA. We observed a noticeable increase of the capacitance equivalent thickness when prepared with CVD-TiN plausibly due to Cl from the source gas. (C) 2001 The Electrochemical Society.