Abstract
In this paper, we present a thorough investigation of the physical and electrical characteristics of a SiO 2 /Al 2 O 3 /SiO 2 (OAO) stack film. The crystallization temperature of an aluminum oxide (Al 2 O 3 ) material of 9.2nm thickness is about 925 °C, and leakage current is determined by trap-assisted tunneling (TAT) in the low E-field region owing to grain boundary formation. Nevertheless, crystalline Al 2 O 3 can increase dielectric constant, lower band gap, and cause offset of conduction band (δE C ); thus, a lower leakage is obtained in high E-field region. Comparing various films with the scheme of SiO 2 /Al 2 O 3 /SiO 2 and presented at various post deposition annealing (PDA) temperatures, it is found that the top oxide thickness and crystallization temperature of the Al 2 O 3 material play key factors for high electric strength and electron trapping. Our experiment demonstrated that a specific SiO 2 /Al 2 O 3 /SiO 2 stack film incorporated with an appropriate thermal budget for Al 2 O 3 annealing can be utilized for future NAND flash memory cells. © 2009 The Japan Society of Applied Physics.