Comparison of the Reliability of Thin $hbox{Al}_{2} hbox{O}_{3}$ Gate Dielectrics Prepared by In Situ Oxidation of Sputtered Aluminum in Oxygen Ambient With and Without Nitric Acid Compensation

摘要

The electrical characteristics and reliability of the aluminum oxide $( hbox{Al}_{2}hbox{O}_{3})$ metal–oxide–semiconductor (MOS) capacitors were investigated under low-temperature process consideration. The simple cost-effective technique in preparing the $hbox{Al}_{2}hbox{O}_{3}/hbox{SiO}_{2}$ bilayer structure as the high-$k$ gate dielectrics was demonstrated in this paper. $hbox{SiO}_{2}$ was prepared by room-temperature anodic oxidation, and $hbox{Al}_{2}hbox{O}_{3}$ was fabricated by room-temperature in situ natural oxidation during the dc sputtering of aluminum in $hbox{Ar/O}_{2}$ ambient. Compared to the $hbox{Al}_{2}hbox{O}_{3}$ MOS capacitors without nitric acid $(hbox{HNO}_{3})$ compensation, significant improvements in electrical characteristics, reliability, and uniformity were achieved by utilizing $hbox{HNO}_{3}$ to moderately oxidize the existing $ hbox{Al}_{2}hbox{O}_{3}$ layer. In addition, the charge trapping behaviors of our samples were also studied by time-dependent dielectric breakdown under the 1000-s constant voltage stress and constant current stress tests. It was found that the electron trapping is dominant under a low negative bias stress. However, under a high negative bias stress, the $hbox{Al}_{2}hbox{O}_{-n-n3}$ MOS capacitors show hole trapping due to the impact ionization near the $ hbox{SiO}_{2}/hbox{Si}$ interface. The in situ oxidation in sputtering with $hbox{HNO}_{3}$ compensation is suitable for future low-temperature dielectric applications.