Study on the characteristics of alumdinum thin films prepared by atomic layer deposition

Abstract

The characteristics of aluminum (Al) films prepared by the atomic layer deposition (ALD) technique using trimethylaluminum (TMA) and a hydrogen plasma were examined for use as a wetting layer for the two-step cold/warm Al deposition. The most important role of a hydrogen plasma was to act as a reducing agent for TMA. The growth rate was saturated at 0.15 nm/cycle, demonstrating that the thickness can be precisely controlled by the number of cycles. Initial layer-by-layer growth was observed and this continued for up to 50 cycles (∼7.5 nm). The root-mean-square thickness variation of an Al film deposited in five cycles (∼0.75 nm) was found to be 0.188 nm. As the PH2/PTMA injection ratio was increased to 10 at a buffer line, the carbon concentration decreased to 1–3 at. %. The resistivity of a 100-nm-thick Al film was 10 μΩ cm and this film was polycrystalline in nature. ALD Al films also had good step coverage on high aspect ratio trenches.