The successful production of Si wafers with a diameter up to 12 inches and a small thickness of ~100 µm has led to the establishment of laser dicing as the primary tool for separation of individual chips. In order to provide high quality devices, manufacturers must take account of the heat affected zone as well as the redeposited layer grown by the ablated material. In general, investigations so far include transmission electron microscopy and 3-point bending to characterize the microstructure and mechanical strength . In this contribution the local residual stress within the redeposited layer was quantified using cross-sectional X-ray nanodiffraction, performed at the synchrotron light source ESRF in Grenoble. Local gradients of residual stress and full width half maxima were evaluated between device front- and backside. Complementary characterization of microstructure in transmission electron microscopy could identify small metallic precipitations within the redeposited polycrystalline silicon layer as origin of these phenomena. It is assumed that this causes the reduced backside breaking strength reported on in similar laser diced devices, reported on in literature .
|Published - 24 Apr 2023
- Semiconductor Processing
- Synchrotron X-ray Diffraction
- Laser Dicing
- Residual Stresses