Effects of NH3 plasma treatment on methyl silsequioxane for copper multi-level interconnect

Abstract

We have tried to modify the surface of methylsilsequioxane (MSQ) by NH3 plasma treatment, As a result, the mechanical hardness of the surface of MSQ increases from 0.242 to 0.419 GPa as the NH3 plasma treatment temperature is increased from 150 to 350degreesC, which is important for chemo-mechanical polishing process. The dielectric constant (k) and surface energy are also fairly improved by the NH3 plasma treatment because the NH3 plasma break's Si-O and Si-CH3 bonds, resulting in lower k, and then nitrogen atoms reduce the imperfect dangling bonds, forming Si-N bonds. However, the NH3 plasma treatment at 350degreesC raises the k value of the MSQ since more nitridation occurs at the higher temperature for long time. The leakage Current density of Cu/MSQ/Si can be reduced as low as 7 orders of magnitude after the NH3 plasma treatment.