Papers by Author: L. Chouanine

Abstract: The effect of the surface properties on the microtribological characteristics of AlN-based electrostatic chuck (EC) for silicon plasma etching was investigated using automatic microscratch testing technique in combination with SEM examination of the scratch track. The scratch testing was performed by applying a progressive indenter load. The scratch failure model varied systematically with the surface properties of AlN. The data of the onset of brittle fracture were used as characteristic features of the AlN failure. It was found that the critical load, Lc, the smallest applied normal load leading to unacceptable damage such as chipping and cracking, increases with decreasing the average grain size, density and fracture toughness of AlN and decreases with increasing the surface roughness and area density of pre-existing polishing damages. The resistance to cohesion and adhesion failure of AlN with 0.1 µm Al2O3 oxide layer on top was stronger than that of the AlN bulk material. The fracture initiation and ductile to brittle transition in AlNAl2O3( 0.1µm) was in form of discontinuous chipping. The results infer the potential of the combination of the scratch data with the material properties for the understanding of the effect of the surface topography on the mechanical properties and chucking performance of AlN-based EC.

Abstract: A microtibological study of the effect of the CMP machining surface damages (SD) on the micromechanical properties of AlN electro-static chuck (ESC) for silicon plasma etching is presented. AFM and SEM examinations of the AlN ESC, which were CMP finished to a surface roughness, Ra = 20 nm, have revealed machining geometry errors and chemical mechanical SD caused by the CMP slurry. The elastic modulus (E) and hardness (H) of AlN and those of yttrium (Y) particles were discretely clarified using localized nanoindentation technique. The results showed that the CMP machining SD fatally affected the AlN/Y boundary strength and resulted to errors in the first contact points between the indenter and the sample. In addition to SD, the micro scale viscoelasticity phenomena of AlN in indentation caused peculiarities at peak loads in the load vs. depth plots. Under these circumstances, the values of E and H measured using Oliver and Pharr's method are in fact underestimated; E = 400 GPa and H = 20 GPa for AlN particles, 300 GPa and 17 GPa for Y particles and 500 GPa and 16 GPa for AlN/Y interface, respectively.

Abstract: A computer program of the fractal analysis by the box-counting method was developed for the estimation of the fractal dimension of the three-dimensional fracture surface reconstructed by the stereo matching method. The image reconstruction and fractal analysis were then made on the fracture surfaces of materials created by different mechanisms. There was a correlation between the fractal dimension of the three-dimensional fracture surface and the fractal dimensions evaluated by other methods on ceramics and metals. The effects of microstructures on the fractal dimension were also experimentally discussed.