Mechanism of charging damage during interlevel oxide deposition in high-density plasma tools

Monte Carlo simulations of pattern-dependent charging during interlevel dielectric (ILD) deposition in high-density plasmas reveal that the initial conformality of the ILD film plays a crucial role in metal line charging and the subsequent degradation of the buried gate oxide to which the metal line is connected. Line charging occurs when the top dielectric is thick enough to prevent tunneling currents, while the sidewall dielectric thickness still allows tunneling currents to flow to the metal line; the differential charging of the sidewalls, which induces the latter currents, is caused by electron shading. The results suggest that charging can be reduced by depositing a more conformal ILD film around the metal line and/or by increasing the film surface conductivity.