Gate Oxide Quality of DRAM Trench Capacitors

The quality of thin trench capacitor oxide dielectric for 4M and 16M DRAM generations is investigated by leakage current and time dependent dielectric breakdown measurements. Geometric trench shape and surface smoothness influence leakage currents and thus di- electric lifetime, but etch chemistry, side wall redeposition and contamination are more important factors which reduce gate oxide quality. It is shown that silicon removing post treatments regain gate oxide quality comparable to planar capacitors.