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Gate oxide engineering

This activity concerns the development of MOS transistor gate oxides with an emphasis on the following three topics (high-k, embedded nanocrystals, single nanocrystal). A fourth topic deals with the efforts in metrology necessary for studying these structures at the nanometer scale.

1) For the success of scaling in the semiconductor industry, it is a great challenge to find new generations of gate dielectrics in MOSFET. Materials with high dielectric constant - high-k - are concerned. The case of thin rare earth oxide films prepared by atomic layer deposition is considered.

REALISE European project

2) Gate oxide engineering is performed by embedding nanocrystals in the oxide in order to give to the MOS transistor new functions implying charge storage (non volatile memories), light emission (electroluminescent devices) or for plasmonic applications

The ANR project “ NOMAD”

3) To avoid or to control averaging effect due to size and shape dispersion, it is interesting to localize a small amount or even one nanocrystal. We try to control, in collaboration with different partners, the number of Si-NCs by implanting Si ions through nanometer size apertures (stencil or block copolymer masks). Our aim is to study quantized charge effects and specific optical properties.

4) As properties of the transistors are to be studied at the nanometer scale, developments in nano-metrology methods are necessary.
- The direct imaging of the atomic structure associated with the local chemical analysis is investigated by transmission electron microscopy measurements in the high resolution mode coupled with electron energy loss spectroscopy in the STEM mode - HRTEM/STEM-EELS.
- Thin layers and interfaces are also investigated using acoustic phonons as internal probes at nanoscale.

Mechanical, structural and chemical properties are accessed combining Raman scattering measurements and simulations.
- Parameters of Si nanoparticle populations (density and size) embedded in a silica matrix can be measured with accuracy only from filtered images - EFTEM.
- Photoluminescence spectroscopy is used also to determine the average size of silicon nanocrystals, and the quality of the surrounding silica matrix.