"Electrical and Physical Characterization of Materials
for the Scaling of
Douglass Buchanan, University of Manitoba, Canada
The scaling of CMOS devices into the nanometer regime has required the introduction of new materials in field effect transistor fabrication. Foremost of these is the introduction of new gate dielectrics to replace the ultra-thin SiO2 films traditionally used. It has been found that HfO2 and variants thereof have been found to reduce gate leakage currents by 2–5 orders of magnitude. Unfortunately these new high-κ materials have also resulted in substantial electron and hole mobility reduction. However, with careful control of the interface growth and in some cases the introduction of strained silicon has led to improvements in mobility. Further increases in electron and more importantly hole mobility have been discovered with the use of silicon substrates of either (110) or (111) orientations or with the introduction of other substrates including Ge and GaAs among others. In combination with high-k dielectric materials, the introduction of metal gates has allowed scaling to continue by eliminating the capacitance of the poly- Si gate. Even though the requirements for such metal gates are quite restrictive, a number of candidates have been found however tailoring of the work-function and band offset of these materials has become paramount.
In the present work I will discuss some of the work that my group has undertaken in the last few years looking at the physical and electrical properties of sputtered HfO2 thin films for gate dielectrics and nitrogen “doped” molybdenum silicide films as a gate metal. This work includes the deposition of thin films and physical and electrical measurement, analysis and ultimately control of the interface region down to and including sub 1nm films. This work also entails the analyses of electronic defects and trapping in these thin films. Finally a discussion of the measurement (through internal photo-emission) and control of the metal gate work-function will be presented and discussed.
Douglas A. Buchanan received the B.Sc. (EE), and M.Sc. degree from the University of Manitoba, Winnipeg MB Canada in 1981 and 1982, respectively. He received his Ph.D. (Applied Physics and Electronics) from the University of Durham, Durham U.K. in 1986
From 1986-2002, he worked for the IBM Research division at the T.J. Watson Research Center and for IBM’s Microelectronics division where he worked on thin film transistors for displays, dielectric and insulator physics and CMOS generations from 0.25 um through to 65 nm. In 2002, he returned to the University of Manitoba where he a professor and Associate-head (Graduate Programs) in the Department of Electrical and Computer Engineering, Dr. Buchanan holds the Canada Research Chair in Microelectronic Materials. His research interests include materials and devices for advanced silicon-based technologies, micro-fluidics systems in silicon for lab-on-a-chip applications, olfactory sensor design and integration and MEMs-based ultra-sonic transducers and sensors.