International audienc

+3620 361 7876This paper suggests the evaluation of morphological parameters of porous silicon layers (PSL) using spectroscopic ellipsometry from UV to midinfrared optical range. PSL were prepared by electrochemical etching of monocrystalline silicon wafers in hydrofluoric acid-based electrolyte. Measuring with an optical and an infrared ellipsometer with a wide spectral range permits an accurate characterization of PSL properties from the top surface to the bottom of the layer with thicknesses from several hundred nanometers up to a few tens of micrometers. Several different optical models for ellipsometric evaluations were developed to determine the thickness, the average porosity, the in-depth porosity gradient, the oxidation level and the surface roughness of the PSL. Porosity was modeled with multiple effective medium layers by varying ratio of crystalline silicon, void and oxidized silicon wherever needed. Thin PSL (< 5 μm) shows no impact of current density on porosity and thickness. However, evaluation of thick PSL (20 -50 μm) highlights the in-depth porosity gradient. Thickness values were also cross-checked with electron microscopy confirming the proposed ellipsometric models. Additionally, different oxidation techniques have also been compared in terms of oxidation level and void content. Volume expansion during PSL oxidation follows exactly the same behavior as that during the oxidation of planar silicon wafers.

The evolution of porous silicon (PSi) from its early studies in the late 70’s toward its industrial application in microelectronics is described in this article. The way this material can be integrated now in many devices at a wafer level is shown in this paper through examples of prototypes that include PSi in their fabrication process. For instance, realization of devices on large area wafers in the field of RF passive components, energy micro-sources or porous flexible membranes are described. In this paper, we also show recent advances in the field of PSi etching and integration at an industrial level. In particular, we put an emphasis on reproducibility and homogeneity issues, on the wafer warp management using different annealing procedures.

This paper deals with the synthesis of high-magnetization porous silicon-based nanocomposites. Using well-controlled organometallic synthesis of ferromagnetic FeCo nanoparticles, the impregnation of mesoporous silicon has been performed by immersion of porous silicon in a colloidal solution. The technique was optimized by controlling the temperature, the immersion duration, and the solvent nature. The characterization of the nanocomposites showed a homogeneous filling of the pores and a high magnetization of 135 emu/cm3. Such composites present a great interest for many applications including data storage, medical instrumentations, catalysis, or electronics.

International audienc

Iron–mesoporous silicon nanocomposites are synthesized by anodization and surface-state assisted electrochemical deposition. Magnetic anisotropy and coercivity are found to depend on the morphology of the iron inclusions.

No abstract

A Backside Silicon-Embedded Inductor (BSEI) surrounded by porous silicon (PS) is reported for quality factor (Q) improvement. Successful formation of a conformal PS layer surrounding deep trenches (where the inductor coil is accommodated) is demonstrated. Experimental results show that although the DC resistance of the BSEI surrounded by PS is 73% higher than the conventional BSEI due to the non-optimized process, a 24% improvement in the peak Q and an 86% increase in the peak Q frequency can be achieved.