Inspection of Charge Effect on Metal Layer by Using SCM

Abstract

The importance of charging damage grows as the IC industry continues downward scaling. It was found that electrical test on metal pad to check contact failure, layer connection and resistance caused charging damage as serious as plasma charging. As for the side effect of it, DC charge is accumulated on the metal TEG, which causes some failure such as incomplete etch problems in the next metal fabrication. This paper provides that charge effect on metal surface is able to be verified by Scanning Capacitance Microscope (SCM). SCM has been used to analyze carrier trap on semiconductor layer in 2D mapping image as well as dopant distribution. In this paper, we will present SCM as more effective and sensitive than contact based DC-EFM (Electrostatic Force Microscope) and verify how to detect the charge on the surface of metal with a physical model based on a parasitic capacitance. It is possible to analyze MIM (Metal-Insulator-Metal) structure because permittivity of insulator is varied like MOS (Metal Oxide Semiconductor) for induced dielectric dipole polarization. Even though it is required to deposit additional insulator layer on a metal, it is highly beneficial to inspect charge effect during post-processing.