Dominic J. Schepis

Limits of Gate Dielectrics Scaling

Abstract This chapter discusses limits of gate dielectric scaling for advanced metal oxide semiconductor field effect transistor (MOSFET). We will review details of hafnium oxide (HfO2) gate oxide and how HfO2 can be modified to hafnium oxynitrides (HfON) and hafnium lanthanum oxynitrides (HfLaON) to increase dielectric constant for continuous equivalent oxide thickness (EOT) scaling. Bilayer hafnium oxide/titanium oxide (HfO2/TiO2) as a higher ‘k’ dielectric option for FinFET gate length (Lg) scaling is discussed. Interfacial layer (IL) scaling technologies for overall EOT scaling are also covered in this chapter. Ab-initio modeling results to evaluate ternary and quaternary gate oxide for higher ‘k’ dielectrics options, and effective metal work functions calculations to optimize and develop new metal gates are discussed. New gate dielectric reliability failure mechanisms due to three dimensional natures of FinFET devices are reviewed. Thermal oxide equivalent quality deposited silicon dioxide (SiO2) using atomic layer deposition (ALD) with post-treatments (e.g., plasma nitridation and anneals) as a high voltage input/output (I/O) gate oxide with silicon-germanium channel (SiGe) results are shown. Finally, we give a brief overview of silicon germanium pFET channel material as a gate dielectric scaling knob, and how it can enable continued EOT scaling without reliability degradation.

Optical band gap analysis and modeling for ultra-thin high-k dielectrics in high-k/metal gate transistors

A highly precise band gap measurement based on deep UV spectroscopic ellipsometry along with Bruggeman effective model approximation was developed for high-k/metal gate CMOS with ultrathin EOT (<1.5u2009nm). By applying and comparing the measurement for HfO2 on SiO2 and SiON interfacial layers with different thicknesses, N%, and annealing conditions, two new sub band gap states corresponding to nitrogen in the film are observed. Together with X-ray photoelectron spectroscopy and electrical measurements, it is found that the band gap energies can be correlated to N% and the leakage current of the high-k films by linear regression (R2 = 0.95). This indicates that the method is capable of quantifying physical and electrical properties of high-k dielectrics, and therefore a time consuming physical analysis or expensive electrical test on fully built devices for gate dielectrics can be avoided.A highly precise band gap measurement based on deep UV spectroscopic ellipsometry along with Bruggeman effective model approximation was developed for high-k/metal gate CMOS with ultrathin EOT (<1.5u2009nm). By applying and comparing the measurement for HfO2 on SiO2 and SiON interfacial layers with different thicknesses, N%, and annealing conditions, two new sub band gap states corresponding to nitrogen in the film are observed. Together with X-ray photoelectron spectroscopy and electrical measurements, it is found that the band gap energies can be correlated to N% and the leakage current of the high-k films by linear regression (R2 = 0.95). This indicates that the method is capable of quantifying physical and electrical properties of high-k dielectrics, and therefore a time consuming physical analysis or expensive electrical test on fully built devices for gate dielectrics can be avoided.