Nano-scale feature analysis achieving high effective lateral resolution with micro-scale material characterization techniques: Application to back-end processing

摘要

Achieving higher performances of electronic devices was first realized by decreasing feature size followed by the introduction of new materials and the switch from planar devices to non-planar ones. Unfortunately, many characterization techniques do not reach lateral resolution compatible with device sizes. This is the case for energy dispersive X-ray spectroscopy (EDS). X-ray photoclectron spectroscopy (XPS), Rutherford backseattering spectrometry (RBS). or time of flight) secondary ion mass spectrometry (TOF-)SIMS. This, however, does not render these techniques useless for small size analysis. This is demonstrated in separate examples taken from back-end of line processing. In back-end, trenches to be tilled with metal lines are etched. This process leaves residues on thernsurfaces that need to be cleaned. XPS is an adequate technique to analyze the chemical composition of (remaining) surface components but does not have the resolution needed to investigate single lines. By using periodic structures and a mathematical model, the composition of the top, sidewall and bottom of the trenches can be easily identified. Once formed, these trenches need to be filled with metallic copper. Due to the small size of the lines, the copper filling is prone to voids formation, which has to be avoided. A good estimation of the presence of void can be achieved using EDS while, intrinsically, the lateral resolution is typically significantly worse than the line dimensions.