Integrated barrier/plug fill schemes for high aspect ratio Gb DRAM contact metallization

Abstract

New contact fill integration schemes were developed for high aspect ratio Gb DRAM contact metallization. Integration schemes for both tungsten-plug contacts and aluminum-plug contacts were studied. For tungsten-plug contacts, various types of titanium liners and titanium nitride barriers were investigated and evaluated. These included collimated PVD (physical vapor deposition) titanium, ion metal plasma (IMP) titanium, and CVD (chemical vapor deposition) titanium liners; plasma enhanced CVD (PECVD) titanium nitride and plasma enhanced MOCVD (ECVD) titanium nitride barriers. The electrical results of 0.3 μm, 5:1 aspect ratio (AR) contact structures processed with a TiCl 4-based CVD titanium liner and plasma enhanced CVD titanium nitride barrier show the lowest and the most tightly distributed contact parametrics. This is attributed to the conformal nature of the CVD process. In addition, the high titanium-deposition temperature, which leads to a simultaneous titanium silicide formation during the CVD titanium deposition process, may also have attribution to the low contact resistance and diode leakage obtained. In the case of aluminum-plug contacts, two different types of titanium nitride barriers (ECVD titanium nitride vs. silane-treated MOCVD titanium nitride) were evaluated and both showed comparable contact parametrics.