Rotational grinding of silicon wafers—sub-surface damage inspection

Industrial practise in wafer manufacturing indicates that there is not one agreed method available to acquire a conclusive picture of the sub-surface damage, defined as structural inhomogeneities of the crystal lattice. Therefore, various methods have been studied and compared for measurement of the sub-surface damage introduced to single crystal silicon wafers during rotational grinding process. Several probing techniques were used to analyse a controlled set of ground silicon wafers. Optical methods were used to study the strain distribution, scattering-in depth and surface topography of the sample set. Acoustic and X-ray diffraction were used to directly observe variations in the Young’s modulus and the lattice constant, respectively. The techniques used ranged from point analysis to whole-wafer mapping and averaging. The study indicates that the various physical properties of the lattice damage arise from closely linked processes taking place during the grinding process. The correlations between the methods included in this study have been identified and quantified, and the relationships between the various observable quantities of sub-surface damage are discussed.