Ultrathin High-k Gate Dielectric Films on Strained-Si/SiGe Heterolayers

Abstract

We have investigated the deposition of alternative gate dielectrics i.e., high dielectric constant (high-k) materials such as ZrO₂ and TiO₂ on strained-Si on relaxed SiGe and strained-SiGe layers. The strained-Si heterolayers generally acquire a high defect density during heteroepitaxy and also the high-k gate dielectric films are prone to point defects. These defects play an important role in determining the electrical properties of the deposited films and their reliability. Basic understanding of the physical and chemical nature of these defects may help to alleviate the reliability problems. In this paper, the nature of several point defects and trap centers created from both strained-Si substrates and high-k gate dielectrics itself has been studied in detail. Magnetic resonance technique has been used to study the chemical nature of the defects present at the interface and dielectric trapping defects present in strained-Si/high-k metal-insulator-semiconductor (MIS) capacitors. The physical nature and the quantification of the trapping/detrapping centers have also been studied under stressing (in both constant current and voltage modes). Time-dependent dielectric breakdown (TDDB) characteristics have been measured to study the reliability of the MIS capacitors.

Indexing terms:

• High-k dielectric
• Defects
• Breakdown
• Reliability
• Strained-Si

Additional information

Notes on contributors

M K Bera

Milan Kumar Bera was born in Midnapore, India, on 1980. He received his BSc and MSc degrees both in Physics from Vidyasagar University, Midnapore, India in 2001 and 2003, respectively. He has completed his PhD work and presently, he is working as a Senior Research Associate in the Electronic Design Automation (EDA) Centre, Department of Electronic Engineering, City University of Hong Kong, Hong Kong. His current research interests include microwave plasma processing/rapid thermal oxidation for ULSI applications, ultrathin oxide, oxynitride, transition and rare-earth based high-k gate dielectric formation on high mobility channel materials such as strained-Si, strained SiGe, Ge-rich SiGe, Ge etc and their characterization, application of strained layers for advanced heterostructure field effect transistors (HFETs) in Si-technology.

C Mahata

Chandreswar Mahata was born in Birbhum, India, on 1981. He received his BSc (2003) degree and MSc, (2005) degree in Physics from Vidyasagar University, Midnapore, India. He is currently working towards the PhD degree. His current research interests include growth and characterization of ultrathin high-k gate dielectrics on high carrier mobility substrate like Ge, strained-Si, SiGe etc for advanced MOSFET application.