Cu is considered as the most promising alternative to Al-based alloy for the interconnection materials in Si-based intergrated circuits due to its low resistivity and superior resistance to electromigration and stress voiding. However, one of the major drawbacks of Cu is its fast diffusion/drift in Si and most commonly used dielectrics, resulting in deterioration of devices at low temperatures. Hence, a diffusion barrier is necessary between Cu and Si.
In this paper, as Cu diffusion barriers, titanium-nitride (Ti-N) and titanium-silicon-nitride (Ti-Si-N) films have been successfully grown by atomic layer deposition (ALD). The film growth kinetics were studied using the concept of ALD and also excellent film characteristics were confirmed.
As a preliminary experiment, Ti-N ALD on $SiO_2$ at the substrate temperature of 200℃ has been investigated by alternate supply of reactant sources, $Ti[N(C_2H_5CH_3)_2]_4$ [tetrakis(ethylmethylamino)titanium: TEMAT] and $NH_3$. Ti-N deposition thickness/cycle was s turated at around 1.6 mono-layers per cycle (ML/cycle) with sufficient pulse times of reactant gases at 200℃. The results suggest that Ti-N deposition thickness/cycle could exceed 1 ML/cycle in ALD, and are explained by the re-adsorption mechanism of the reactant gases. An ideal linear relationship between number of cycles and Ti-N film deposition thickness was confirmed.
Step coverage was excellent, particles may be caused by the gas phase reactions between TEMAT and $NH_3$ were almost absent because TEMAT was separated from $NH_3$ by the Ar pulse. In spite of relatively low deposition temperature, carbon impurity in ALD Ti-N films was incorporated below 4 at.% compared with above 25 at.% in MOCVD Ti-N films.
With the ALD concept from Ti-N ALD using TEMAT and $NH_3$, Ti-Si-N thin films have been grown by ALD using a sequential supply of $Ti[N(CH_3)_2]_4$ [tetrakis(dimethylamido) titanium: TDMAT], ammonia and silane at the substrate temperature of 180℃ and th...