Effect of PVD process parameters on the quality and reliability of thin (10–30 nm) Al2O3 dielectrics

Abstract

Over the last decade, dielectric scaling in non-volatile memories (NVM) and CMOS logic applications has reached a point where better innovations will be required to meet the reliability and performance requirements of future products. For both these applications, high k materials are being explored as possible candidates to replace the traditional SiO 2 and oxide/nitride/oxide-based films used today. While there are several attractive candidates to replace these materials, HfO 2 and Al 2 O 3 are considered as the most promising ones. Although there has been a lot of work on CVD-based Al 2 O 3 , there has not been much reported for PVD-based Al 2 O 3 for NVM applications, especially in the thickness regime of 10–30 nm. This paper discusses the effects of process parameters such a plasma power and annealing conditions on the quality of Al 2 O 3 dielectrics. It was observed that a post deposition anneal in O 2 ambient at 700°C for 15 s is essential to obtain a fully oxidized film with high density. While higher power (1,500 W) results in thicker films with better k values, they also lead to more substrate damage and poorer reliability. Annealing done at temperatures greater than 700°C for 60 s or more results in failure of the film possibly due to diffusion of silicon into Al 2 O 3 and its subsequent reaction.