Swift ion irradiation effect on high-k ZrO₂- and Al₂O₃-based MOS devices

ABSTRACT

This paper describes the heavy ion-induced effects on the electrical characteristics of reactively sputtered ZrO₂ and Al₂O₃ high-k gate oxides deposited in argon plus nitrogen containing plasma. Radiation-induced degradation of sputtered high-k dielectric ZrO₂/Si and Al₂O₃/Si interface was studied using 45 MeV Li³⁺ ions. The devices were irradiated with Li³⁺ ions at various fluences ranging from 5 × 10⁹ to 5 × 10¹² ions/cm². Capacitance–voltage and current–voltage characteristics were used for electrical characterization. Shift in flat band voltage towards negative value was observed in devices after exposure to ion radiation. Post-deposition annealing effect on the electrical behavior of high-k/Si interface was also investigated. The annealed devices showed better electrical and reliability characteristics. Different device parameters such as flat band voltage, leakage current, interface defect density and oxide-trapped charge have been extracted.The surface morphology and roughness values for films deposited in nitrogen containing plasma before and after ion radiation are extracted from Atomic Force Microscopy.

KEYWORDS:

• Al₂O₃
• swift ion radiation
• high-k
• ZrO₂

Acknowledgements

The authors would like to express their sincere thanks to Prof. Somenath Biswas, Director, IIIT/Allahabad for his constant support and encouragement. Thanks are also due to Dr K. Asokan, IUAC, New Delhi, India, for providing the ion radiation exposure facility. The authors also thank Mr Pramod Tripathi and Mr Upendra Joshi technical staff, for their assistance.

Disclosure statement

No potential conflict of interest was reported by the authors.