Investigation of high-K dielectric films incorporated with Lanthanum and their application in flash memory devices

Abstract

High permittivity dielectrics (LaAlOx and HfLaOx) deposited using atomic layer deposition (ALD) were investigated as blocking oxide in SONOS-type flash memories for improved tradeoff between data retention and operation speeds. The ALD process parameters and material properties of these lanthanum- incorporated dielectrics were investigated systematically, focusing on HfLaOx films with 8 % La which had the highest permittivity of 38. However, the SONOS-type flash memory cells with HfLaOx blocking oxide showed degraded data retention. In contrast, flash memory cells with LaAlOx blocking oxide exhibited improved data retention at temperatures below 120?C. Furthermore, all other memory characteristics were also improved, such as speeds, saturation window, and reliability. The trapping energy depth in nitride film and the dependence of data retention was also studied in depth. Overall, LaAlOx is a promising candidate as a blocking oxide to further boost flash memory performance.