THE OXIDATION MECHANISM OF LOW-PRESSURE DRY OXIDATION OF NITRIDES FORMEMORY DEVICES

To be utilized in the high density dynamic random access memory device s, low-pressure dry oxidation of the very thin nitrides has been perfo rmed to successfully obtain the ultrathin capacitors' dielectrics with the effective oxide thickness (t(ox,eff)) of 30 - 60 Angstrom. For th e electrical properties, the low-pressure dry oxidized (LPDO) nitrides express thinner effective oxide thickness, lower leakage current, and higher reliability than do the atmospheric pressure dry oxidized (APD O) nitrides. After analyzing the diluted HF etching profiles, Auger el ectron spectrum and Fourier transform infrared spectrum data, an oxide /nitride/oxide (O/N/O) structure is realized for the LPDO samples with respect to the nitride/oxide structure for the APDO ones. This ultrat hin O/N/O structure is believed to be the main cause of improving the electrical characteristics. Finally, a low-pressure enhanced oxidation model is also proposed to explain the unusual oxidation phenomenon on the top of the nitride films. The mechanisms of APDO and atmospheric pressure wet oxidation of nitride films are also compared.