Analysis of silicon wafer damage due to nanoindentation by microraman spectroscopy and white beam synchrotron X-ray toporaphy

In the semiconductor industry, wafer handling introduces micro-cracks at the wafer edge and the causal relationship of these cracks to wafer breakage is a difficult task. By way of understanding the wafer breakage process, a series of nano-indents were introduced to both 20 x 20mm (100) wafer pieces and into whole 200mm wafers as a means of introducing controlled strain. The indents were introduced to the silicon by way of a Berkovich tip with applied forces of 100mN to 600mN and with a Vickers tip with applied forces of 2N to 50N. The samples were subjected to an array of both in situ and ex situ anneal in order to simulate a production environment. The samples were analysed using both micro-Raman spectroscopy and white beam x-ray topography to study the strain fields produced by the nano-indentation and the effect of annealing on the strain fields which was then compared to FEM models of the indents. A novel process for the creation of three dimensional x-ray images, 3D-XRDI, was defined using ImageJ, a freely available image processing tool. This allowed for the construction of three dimensional images and the ability to rotate these images to any angle for ease of viewing. It will be shown how this technique also provided the ability to travel through the sample to view the dislocation loops at any point within the sample. It was found that the temperature profile across the annealing tool had an effect on the strain fields, the growth and movement of dislocation loops and slip bands and on the opening and propagation of cracks. The behaviour of the cracks during rapid thermal anneal was also observed and from this data a parameter was defined that could predict the possibility of wafer breakage.