HIGHLY RELIABLE FLASH MEMORIES FABRICATED BY IN-SITU MULTIPLE RAPID THERMAL-PROCESSING

We propose, for the first time, highly reliable flash-type EEPROM cell fabrication using in-situ multiple rapid thermal processing (RTP) tec hnology. In this study, rapid thermal oxynitridation tunnel oxide (RTO NO) film formations followed by in-situ arsenic (As)-doped floating-ga te polysilicon growth by rapid thermal chemical vapor deposition (RTCV D) technologies are fully utilized. The results show that after 5 x 10 (4) program/erase (P/E) endurance cycles, the conventional cell shows 65% narrowing of the threshold voltage (V(t)) window, whereas the RTON O cell indicates narrowing of less than 20%. A large number of nitroge n atoms (approximately-greater-than 10(20) atoms/cm3) are confirmed by secondary ion mass spectrometry (SIMS), pile up at the SiO2/Si interf ace and distribute into bulk SiO2. It is considered that in the RTONO film stable Si-N bonds are formed which minimize electron trap generat ion as well as the neutral defect density, resulting in lower V(t) shi fts in P/E stress. In addition, the RTONO film reduces the number of h ydrogen atoms because of final N2O oxynitridation. The SIMS data shows that by the in-situ RTCVD process As atoms (9 x 10(20) atoms/cm3) are incorporated uniformly into 1000-angstrom-thick film. Moreover, the R TCVD polysilicon film indicates an extremely flat surface. The time-de pendent dielectric breakdown (TDDB) characteristics of interpoly oxide -nitride-oxide (ONO) film exhibited no defect-related breakdown and 5 times longer breakdown time as compared to phosphorus-doped polysilico n film. Therefore, the flash-EEPROM cell fabricated has good charge st oring capability.