Aluminum spiking at contact windows in Al/Ti-W/Si

Abstract

Aluminum spike formation through a Ti-W interdiffusion barrier layer at contact windows is studied by cross-sectional transmission electron microscopy for Al-1% Si and Al-2% Cu films. For Ti-W layers thinner than 1000 Å Al spikes form in both Al-Si and Al-Cu systems. The two types of Al films behave similarly in terms of the propensity for spike formation and spike morphology in the presence of a Ti-W layer. Aluminum spikes generally have an inverted pyramidal, truncated inverted pyramidal, or parallelepipedal shape. Aluminum in a spike is generally single crystal and some of the Al spikes maintain one of the following orientation relationships with the surrounding Si substrate: [011]Al∥[1̄23]Si and (200)Al∥(11̄1)Si or [001]Al∥[1̄12]Si and (200)Al is 2° off (11̄1)Si. A mechanism for Al spike formation through Ti-W is proposed.