The application of MEIS for the physical characterisation of high-k ultra thin dielectric layers in microelectronic devices

Reading, MA

Abstract

During the last decade the use of 8162 as gate dielectric layers in complementary
metal oxide semiconductor (CMOS) microelectronic devices has become increasingly
problematic due to leakage resulting from the electron tunnelling with gate oxide
thickness approaching 1 nm. Approaches to deal with these problems have focused on
increasing the dielectric constant (k) of the material, initially though nitridation of the
oxide layer and more recently the application of high-A: materials such as Hf based
dielectrics. The work described in this thesis concerns the physical characterisation of
thin high-A: multilayered samples using medium energy ion scattering (MEIS). A MEIS
computer simulation model was applied and adapted to enable the interpretation of
depth profiles from MEIS energy spectra. Forming part of an EU collaborative project,
results obtained were compared to those of X-ray photoelectron spectroscopy (XPS),
transmission electron microscopy (TEM), and X-ray fluoresence (XRF) to provide a
better overall understanding of the characteristics of the layers.
Nanometre thin SiC>2 layers nitrided using a novel plasma nitridation technique
were investigated, demonstrated the nitridation of, and yielded the N distributions in the
SiC>2 samples as well as demonstrating plasma damage. An improved k value was
found, leading to an increased equivalent oxide (EOT) thickness.
Studies of HfO2 and HfSiOx nanolayers, both with and without subjection to a
decoupled plasma nitridation (DPN) process were carried out, characterising the layer
structures with an accuracy of 0.1 nm in excellent agreement with the additional
techniques. Crystallisation of the HfO2 layers, but not of the HfSiOx layers, after DPN
was demonstrated. A high-A; metal gate Si/SiO2/HfO2/Al2O3/TiN stack was also
investigated and Hf/Al interdiffusion demonstrated upon annealing.
Finally Si/TiN/STO layers grown using different stoichiometric recipes, with
and without a rapid thermal anneal at 650°C for 15s, were analysed. Layer structures
were again determined with sub-nm resolution and diffusion between the Sr and Ti
layers was observed after annealing.
The high level of agreement between the depth profiles derived from the MEIS
energy spectra, the growth parameters and the results from additional techniques has
demonstrated the capability of MEIS in combination with spectrum simulation for the
accurate analysis of these demanding ultra thin layer structures.

Citation

Reading, M. The application of MEIS for the physical characterisation of high-k ultra thin dielectric layers in microelectronic devices. (Thesis). Salford : University of Salford

• Thesis Type: Thesis
• Deposit Date: Oct 3, 2012
• Award Date: Jan 1, 2010