Redistribution of Pt during the agglomeration of NiSi

Due to the constant downscaling of microelectronic devices, thin films of Ni-Pt monosilicide, Ni(Pt)Si, are widely used as contact materials on the active regions of complementary metal-oxide-semiconductor (CMOS) devices. However, Ni(Pt)Si films are highly sensitive to agglomeration during high thermal budget processing, leading to morphological discontinuity and a drastic reduction in the overall yield of microelectronic devices. In this study, the redistribution of platinum (Pt) during the agglomeration of Ni(Pt)Si is investigated using scanning transmission electron microscopy with energy-dispersive X-ray spectroscopy (STEM-EDX) measurements. Results indicate that agglomeration follows the classical steps, beginning with the formation of holes, grain boundary grooving, and finally the expansion of holes, resulting in isolated islands of Ni(Pt)Si. The surface of the sample remains flat, corroborating the particularity of inverse agglomeration in Ni(Pt)Si thin films. Moreover, the complex redistribution of Pt is characterized by the existence of three different regions: a Pt-rich surface region, a Pt-depleted region within the grain, and a moderately Pt-rich region near the silicide/Si interface that corresponds to the displaced Ni(Pt)Si. A model is developed to describe the redistribution of Pt during grooving and agglomeration. These findings have implications for understanding the complex nature of Ni(Pt)Si agglomeration and, especially, the role of Pt in the agglomeration phenomenon.