With the scaling of devices, integration of porous ultra low-k materials into Cu interconnect becomes imperative. Low-k dielectric materials consist of methyl groups and pores incorporated into a silicon dioxide backbone structure to reduce the dielectric constant. Plasma is widely used in semiconductor industry for deposition, etching, stripping etc. This book explores the interaction between plasma and low-k dielectric materials and their application in advanced semiconductor processes. It mainly consists of two parts. First, plasma assists the atomic layer deposition of Ta based Cu barriers. Experiments, coupled with Monte Carlo simulation proved that plasma alters low-k surfaces and generates favorable surface function groups for subsequent Ta/TaN deposition. Second, plasma degrades properties of low-k materials through methyl depletion. Mechanism of plasma damage to blanket and pattern low-k films was discussed. Then techniques for low-k repair, such as methane beam and silylation, were demonstrated.