Annealing Effects on Charge Trap Flash with TAHOS Structure

Abstract

Flash memory is gaining attention due to its scalability, high reliability, and multilevel capabilities. This study investigated the charge trapping characteristics of high permittivity HfO2 films with Al2O3 as a blocking oxide. TAHOS (TiN-Al2O3-HfO2-SiO2-Si) structure capacitors were fabricated to explore the annealing effects for charge trap flash (CTF) memory device applications. HfO2, serving as a charge trapping layer, offers the advantage of achieving a wide memory window owing to its high trap density. In this work, various characteristics related to memory cells were examined based on annealing temperature and gas type. Post-deposition annealing (PDA) was conducted from 900 °C to 1050 °C and forming gas annealing (FGA) was performed at 450 °C for 10 minutes using H2 gas. We analyzed the memory window and flat-band voltage distributions by measuring C-V characteristics. These results suggest that optimal annealing conditions can be helpful to improve memory characteristics in TAHOS stacked flash memories.