ABSTRACT
CONTENTS 10.1 Introduction ...................................................................................................................... 305
10.1.1 Differences between High-K, SiO2, and Si Oxynitride Gate Dielectrics ..... 306 10.1.2 Roadmap for This Chapter................................................................................ 308
10.2 Spectroscopic Studies of Thick (>4 nm) High-K Nanocrystalline Dielectrics ........ 308 10.2.1 Spectroscopic Studies of Intrinsic Electronic Structure
in Thick TM Oxides ............................................................................................ 309 10.3 Theory of Defects in Thick HfO2 Nanocrystalline Films ........................................... 316 10.4 Defect Reductions Associated with Dimensional, Kinetic, and Alloy Effects ........ 319
10.4.1 Noncrystalline Films........................................................................................... 319 10.4.2 As-Deposited and Annealed HfO2 Films >4 nm Thick................................ 324 10.4.3 Thin Nanocrystalline Films ............................................................................... 326 10.4.4 HfO2 Films with Bonded Nitrogen .................................................................. 327
10.5 Interface Properties between Si and SiO2 and Si3N4, and Ge between GeO2 and Ge3N4 ................................................................................ 328
10.6 Electrical Measurements and Dielectrics for Radiation Hard Survivable Electronics........................................................................................... 332 10.6.1 Electrical Measurements on Hf-Based Dielectrics.......................................... 332 10.6.2 Options for Hf-Based Radiation Hard Devices
for Survivable Electronics .................................................................................. 337 10.7 Summary........................................................................................................................... 337 Acknowledgments ..................................................................................................................... 338 References.................................................................................................................................... 338
This chapter deals with intrinsic defects in high-K dielectrics attributed to local bonding arrangements that differ from the intrinsic bonding arrangements of the host material independent of whether or not the particular thin-film dielectric is nanocrystalline or noncrystalline. As such this chapter addresses three different areas of experimental and theoretical research: (1) spectroscopic studies of the intrinsic electronic structure of the
theoretical framework for describing electronic structure and the intrinsic bonding defects, and (3) relationships between the defect properties identified spectroscopically, and defect studies on test device structures addressing (a) preexisting defects in as-deposited films, and also (b) noting the importance of defects generated by subjecting the most promising high-K dielectrics for radiation hard survivable electronics to ionizing radiations such as x-rays and g-rays. The field of high-K dielectrics now has been narrowed through about 10 years of
worldwide research and technology studies, and the materials that have received the most attention are Hf-based dielectrics [1], including (1) ultrathin films of HfO2 with a physical thickness of less than about 2 nm [2], and (2) noncrystalline Hf-based alloys, generally characterized as HfSiON [3], and more recently including specific pseudoternary alloy compositions such as (HfO2)x(SiO2)y(Si3N4)1xy, with SiO2HfO2 0.3, and Si3N4 0.4 [4]. There has recently been renewed interest in Zr-based high-K dielectrics, especially in the context of using semiconductor substrates other than Si, strained Si, or Si, Ge alloys for advanced devices [1]. These nonsilicon substrates include Ge, SiC, and III-V semiconductors, such as GaAs [5,6]. There are several excellent published reviews that include discussions of high-K dielec-
trics; the one that is most timely with respect to the subject matter addressed in this chapter is a collection of articles edited by M. Houssa and published by the Institute of Physics in 2004 [1]. There are also many annual conferences sponsored by a wide range of technical societies that include a strong focus on high-K dielectrics as well.
