Comparison of the reliability of thin Al2O3 gate dielectrics prepared by in situ oxidation of sputtered aluminum in oxygen ambient with and without nitric acid compensation
Journal
IEEE Transactions on Device and Materials Reliability
Journal Volume
11
Journal Issue
2
Pages
227-235
Date Issued
2011
Author(s)
Abstract
The electrical characteristics and reliability of the aluminum oxide (Al 2 O 3 ) metal-oxide-semiconductor (MOS) capacitors were investigated under low-temperature process consideration. The simple cost-effective technique in preparing the Al 2 O 3 /SiO 2 bilayer structure as the high- k gate dielectrics was demonstrated in this paper. SiO 2 was prepared by room-temperature anodic oxidation, and Al 2 O 3 was fabricated by room-temperature in situ natural oxidation during the dc sputtering of aluminum in Ar/O 2 ambient. Compared to the Al 2 O 3 MOS capacitors without nitric acid (HNO 3 ) compensation, significant improvements in electrical characteristics, reliability, and uniformity were achieved by utilizing HNO 3 to moderately oxidize the existing Al 2 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 Al 2 O 3 MOS capacitors show hole trapping due to the impact ionization near the SiO 2 /Si interface. The in situ oxidation in sputtering with HNO 3 compensation is suitable for future low-temperature dielectric applications.
Type
journal article