Controlling the composition of doped materials by ALD: A case study for Al-doped TiO₂ films

This study examined the effect of the process sequence on the composition of doped films grown by atomic layer deposition (ALD) by investigating the passivation effect of one precursor on the chemisorption of another in the subsequent step. Considering that Ti (O-i- C3 H7) 4 (TTIP) and Al (CH3) 3 (TMA) do not react with each other, Al-doped TiO2 films were grown by ALD through various process sequences. The film thickness was barely affected by modification of the process sequence. However, the process sequence where TTIP exposure was followed by TMA exposure caused a decrease in the Al/Ti ratio in the Al-doped TiO2 films without altering the Al and Ti precursor cycle ratio, which resulted in an increase in the dielectric constant.