Characterization of Post Etch Residues on Patterned Porous Low-k Dielectric Using Multiple Internal Reflection Infrared Spectroscopy

Plasma etching and ashing processes on intricate porous low-k dielectrics are known to introduce high levels of defects that may cause serious reliability issues. Post etch cleans to remove polymer residues could also further damage the porous low-k dielectrics. Compounding the difficulty of handling weak porous ULK materials, a lack of sensitive metrology to evaluate such damage is a serious hindrance to systematic development of plasma etching, restoration and cleaning processes. In this paper, a new metrology tool using Multiple Internal Reflection Infrared Spectroscopy (MIR-IR) was developed and tested using silicon wafer based IR waveguides. Our data demonstrates the capability of MIR-IR spectroscopy to monitor removal of thin polymeric post-plasma etch residues from porous low-k dielectrics and characterize plasma-induced dielectric damage.