MICROSCOPY Vol.47▶No.2 2012
■Researches Today

Dielectric Constant Measurement of Low-k Interconnect Dielectrics by Valence Electron Energy Loss Spectroscopy (VEELS)

Yuji Otsuka, Naohiko Kawasaki, Hideki Sako and Shinichi Ogawa

Abstract: Electron Energy Loss Spectroscopy (EELS) equipped with Transmission Electron Microscope (TEM) at lower-kV has been carried out for precise characterization of low-k interconnect dielectrics. Structural changes after plasma processes such as dry etch and ashing were characterized by using valence EELS (V-EELS) at lower accelerating voltage such as 80kV. Because the electron irradiation damage and the unexpected effects of Cerencov radiation can be significantly ignored at low-kV VEELS, so that we could derive more precise dielectric constant profile by Kramers-Kronig Analysis (KKA) than characterization at conventional 200 kV. Of course dielectric constant by high energy electron measurement such as TEM only gives electron polarization intensity inherently, however it is useful to characterize the electrical damage structures at high spatial resolution. At the adjacent of the side wall, the peak at 2eV is significantly increased in ε2, it assumed that defects such as silicon dangling bonds were generated during the Cu/Low-k processing. It has been demonstrated that the combination of conventional composition analysis and VEELS at low-kV (80keV) is very useful for characterization of the damages in the patterned Cu / low-k interconnect structure for advanced ULSI processing.

Key words: Valence Electron Energy Loss Spectroscopy,VEELS,low-k,Kramers-Kronig Analysis,Cerenkov radiation