Characteristics of n+ polycrystalline-Si/Al2O3/Si metal–oxide– semiconductor structures prepared by atomic layer chemical vapor deposition using Al(CH3)3 and H2O vapor

Abstract

We report interface and dielectric reliability characteristics of $n^{+}$ polycrystalline-silicon (poly-Si)/${\mathrm{Al}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}\mathrm{/Si}$ metal–oxide–semiconductor (MOS) capacitors. ${\mathrm{Al}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}$ films were prepared by atomic layer chemical vapor deposition using ${\mathrm{Al(CH}}_{\mathrm{3}}{\mathrm{)}}_{\mathrm{3}}$ and ${\mathrm{H}}_{\mathrm{2}}\mathrm{O}$ vapor. Interface state density ${\mathrm{(D}}_{\mathrm{it}})$ and dielectric reliability properties of $n^{+}$ poly-${\mathrm{Si/Al}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}\mathrm{/Si}$ MOS structures were examined by capacitance–voltage, conductance, current–voltage, and time-dependent dielectric breakdown measurements. The $D_{\mathrm{it}}$ of the $n^{+}$ poly-${\mathrm{Si/Al}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}\mathrm{/Si}$ MOS system near the Si midgap is approximately ${\text{8×10}}^{10} {\mathrm{eV}}^{\mathrm{-1}}{\mathrm{ cm}}^{\mathrm{-2}}$ as determined by the conductance method. Frequency dispersion as small as ∼20 mV and hysteresis of ∼15 mV were attained under the electric field of ±8 MV/cm. The gate leakage current of ∼36 Å effective thickness ${\mathrm{Al}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}$ dielectric measured at the gate voltage of −2.5 V is ∼−5 nA/cm², which is approximately three orders of magnitude lower than that of a controlled oxide $({\mathrm{SiO}}_{\mathrm{2}}\mathrm{).}$ Time-dependent dielectric breakdown data of ${\mathrm{Al}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}\mathrm{/Si}$ MOS capacitors under the constant current/voltage stress reveal excellent charge-to-breakdown characteristics over controlled oxide. Reliable gate oxide integrity of ${\mathrm{Al}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}$ gate dielectric is manifested by the excellent distribution of gate oxide breakdown voltage on 128 million MOS capacitors having isolation edges. Extracted time constant and capture cross section of the ${\mathrm{Al}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}\mathrm{/Si}$ junction are discussed.