AVS 52nd International Symposium
    Electronic Materials and Processing Monday Sessions
       Session EM-MoM

Paper EM-MoM3
The Effect of Nitrogen Incorporation on the Material and Electrical Properties of HfO@sub 2@ on Si

Monday, October 31, 2005, 9:00 am, Room 309

Session: Electronic Properties of High-k Dielectrics and their Interfaces
Presenter: M. Sawkar, UCLA
Authors: M. Sawkar, UCLA
J. Choi, UCLA
R. Puthenkovilakam, UCLA
J.P. Chang, UCLA
Correspondent: Click to Email
Alternative gate dielectrics are required in the future generation of MOSFET devices to enable their rapid down-scaling. One of the most promising candidates is HfO@sub 2@. Unfortunately, HfO@sub 2@ has a low crystallization temperature, resulting in its structural change from amorphous to polycrystalline under high-temperature processing, which results in grain boundaries that serve as a path for leakage current, oxygen diffusion, and impurity diffusion. The incorporation of nitrogen in HfO@sub 2@ films increases the temperature at which the grain boundaries form allowing these films to remain amorphous at higher temperatures. This paper discusses the effect of nitrogen incorporation on the material and electrical properties of HfO@sub 2@. XPS, ellipsometry, and HRTEM are used to characterize the material properties. To characterize the electrical properties, MOS capacitors are fabricated to examine the capacitance-voltage (C-V) and current density-voltage (J-V) characteristics. Preliminary results showed that the leakage current density of the nitrogen incorporated samples is approximately three orders of magnitude lower than the as-deposited HfO@sub 2@. We also performed first-principle simulations within the framework of density functional theory to assess the effect of nitrogen incorporation on the bulk electronic properties of HfO@sub x@N@sub y@, as well as on the dielectric/Si interface properties. The simulation shows that the N 2p state is extended further toward the conduction band and the ionic character of Hf-N bonding is less pronounced with increasing nitrogen incorporation, resulting in a reduction in the band gap. The band alignment at the HfO@sub x@N@sub y@/Si interface calculated using the (HfO@sub 2@)(Hf@sub 3@N@sub 4@) structure as a model stoichiometry revealed an estimated valence-band offset of 1.14 eV, which is significantly lower than that reported for HfO@sub 2@/Si.