Investigation of rare-earth aluminates as alternative trapping materials in Flash memories

The integration of La, Gd, and Lu aluminates in a Charge-Trapping Flash (CTF) memory flow as alternative trapping materials is evaluated. It is found that, in order to control the mixing of the aluminates with the tunnel oxide, nitride (for Gd) or nitride + oxide (for La and Lu) buffer layers have to be used. It is also found that during the post-deposition annealing treatments, the nitride buffer layer mixes with the tunnel oxide. This results in very good erase and endurance performance, which is attributed to enhanced hole tunneling from the Si substrate.