Impact of TiN Barrier Layer on Contact Resistance of Tungsten Filled Vias

摘要

In this paper, we directly compare the influence of sputtered and chemical vapor deposited TiN liners on the contact resistance of large tungsten filled vias with an aspect ratio of 3:1. Scanning transmission electron microscopy, energy-dispersive X-ray spectroscopy, and time-of-flight secondary ion mass spectrometry studies revealed that during WF₆-based tungsten chemical vapor deposition (CVD), fluorine diffuses through a poor physical vapor deposited (PVD) TiN barrier layer and reacts with the underlying titanium and aluminum to form high resistive compounds. Aside from depositing a thicker TiN PVD barrier, the replacement of the 40 nm PVD layer with a thinner TiN CVD liner has led to significantly reduced via resistances with very small deviations across the wafer and lot. We show that the CVD layer has a superior barrier performance against fluorine penetration, provides a conformal coverage and can be used at a reduced thickness compared to the PVD process.