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 nonvolatile 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.

Identification of current transport mechanism in Al2O3 thin films for memory applications

“…Current conduction in the ohmic mechanism is governed by a hopping mechanism, where the electrons hop between the defect states present in the dielectric (Perera et al 2003). These defect states could be due to the formation of mobile interstitial Si species (Dutta et al 2011). During the anneal, O 2 diffuses into the dielectric and reacts with the bulk Si at the dielectric-substrate interface.…”

“…Al 2 O 3 has a large band gap (&8.7 eV) (Robertson 2006;Kolodzey et al 2000) and higher crystallization temperature compared to HfO 2 (Robertson 2006;Bouazra et al 2008) and proven electrical characteristics. Hence, it is rightly being pursued for use as blocking dielectric in flash memories (Dutta et al 2011). Fig.…”

A detailed study on frequency dependent electrical characteristics of MOS capacitors with dysprosium oxide gate dielectrics

“…Over last few decades, researchers have devoted great efforts to replace conventional SiO 2 gate dielectric with suitable alternative high dielectric constant (k) material in metaloxide-semiconductor (MOS) based technology [1][2][3][4][5][6][7][8]. The main focus of these studies is to improve MOS based device performance used in the several applications.…”