Impact of plasma power on plasma enhanced atomic layer deposited TiO2 as a spacer

Abstract

As the size of devices is scaled down, micro-patterning technology is increasing in importance. In micro-patterning, spacers require precise thickness and uniform deposition at low temperature. To meet these requirements, atomic layer deposition (ALD), which can be controlled to an accurate thickness, was introduced. Therefore, we investigated plasma-enhanced ALD using radicals for high reactivity. Optical emission spectroscopy and a Langmuir probe were used to evaluate plasma properties such as radical intensity and plasma density at different plasma powers. Regardless of plasma power, growth per cycle and compositions of Ti and O remained constant. X-ray photoelectron spectroscopy showed that application of 500 W decreased the area of Ti₂O₃ from 20.2 % to 4.5 % compared with 100 W due to the increased amount of oxygen radicals. X-ray reflectivity results showed a 4.09 g/cm³ density of TiO₂ film at 100 W, which increased to 4.2 g/cm³ at 500 W, indicating a decrease of Ti₂O₃. Meanwhile, the wet etch rate of TiO₂ film was 1.72 Å/min at 100 W and 0.8 Å/min at 500 W, and the denser film had superior etch resistance. Finally, transmission electron microscopy showed that step coverage of TiO₂ films improved from 90.9 % to 99.9 % with increasing power. Thus, application of high power effectively improved the properties of TiO₂ films.