Phase growth in an amorphous Si-Cu system, as shown by a combination of SNMS, XPS, XRD and APT techniques

It is shown, by the combination of secondary neutral mass spectrometry (SNMS), X-ray diffraction and atom probe tomography (APT), that the growth of a Cu3Si crystalline layer between amorphous Si and nanocrystalline Cu thin films at 408 K follows a linear law and the shifts of the Cu3Si/Cu and Cu3Si/amorphous Si interfaces contribute approximately equally to the growth of this phase. It is also illustrated that the Si atoms diffuse rapidly into the grain boundaries of the nanocrystalline Cu, leading to Si segregation on the outer surface and to an increase in the overall Si content inside the Cu layer. Both the SNMS and APT results indicate that, even during the deposition of Cu on the amorphous Si, an intermixed region (of about 10 nm thick) is formed at the interface. This readily transforms into a homogeneous Cu3Si crystalline reaction layer which grows further, apparently following an interface-controlled linear kinetics.