Optimization of precursor pulsing in atomic layer deposition

Abstract

In this work aluminium oxide (Al2O3) and tanalum oxide (Ta2O5) films are grown by atomic layer deposition (ALD) on silicon substrates. The research was performed at Micro and Nanosciences Department of Helsinki University of Technology. The effect of precursor pulsing time and pulsing method on film growth rate, mean thickness and thickness variations was studied. The film thickness was measured with ellipsometry.

The modelling of precursor pulsing time was presented. The simulation of trimethylaluminum (TMA) pulsing pressure with different pulsing time was carried out. The results indicated that the pressure before the pulsing valve decreases to a steady state if the valve open time was long enough.

In TMA and H20 optimization experiments, the growth rate of 1.2 Å/cycle and thickness variation of 0.4 % were achieved with 100 ms H20 pulsing time at a temperature of 220 °C. In TaC15 and H20 experiments, 0.8 Å/cycle growth rate and 4.6 % thickness variation obtained with 25 ms TaC15 pulsing time at 200 °C. In the TaC15 pulsing mode optimization experiments, the same growth rate of 0.8 Å/cycle was acquired with booster pulse mode and combination pulse mode.