Electrical characterization of low permittivity materials for ULSI inter-metal-insulation

The ever increasing demand for high performance integrated devices results in more and more low dielectric constant materials being proposed to replace silica for interconnects insulation. We present results concerning two organic materials (Flare and SiLK) and one mineral (porous silica). These materials present good dielectric characteristics when dry, i.e. they have a very low leakage current and a long breakdown time to failure. However, moisture uptake weakens their characteristics. The leakage current is increased, but generally not in a crucial manner. More critical is the drastic decrease of the breakdown time to failure. This sensitivity must be taken into account both in wafer encapsulation design and during the process of eliminating residual moisture before encapsulation of each low-k material layer. (C) 2000 Elsevier Science Ltd. All rights reserved.