Detection of nanoscale etch and ash damage to nanoporous methyl silsesquioxane using electrostatic force microscopy

We have used electrostatic force microscopy (EFM) to detect nanoscale dielectric constant variations resulting from damascene processing of blanket and patterned films of nanoporous methyl silsesquioxane (MSQ) (k = 2.2). Ash processing can cause significant degradation of the dielectric constant for both blanket and patterned MSQ films if the film is exposed to moisture. We have observed that this degradation is reversible because the apparent dielectric constant of the ashed film is nearly the same as the as-deposited film if the film is baked at 80–150 °C. Reactive ion etching (RIE) causes ∼100 nm deep side wall damage in patterned samples as well as leaving a redeposited layer that has a higher dielectric constant. We also present some initial results that show the strength of the EFM signal is humidity dependent.