The aim of this study was to evaluate the effects of process temperature and pressure on the Al2O3 ALE process. The results showed that the etch rate of the aluminium oxide is dependent on process temperature and pressure.
The Al2O3 ALE process was performed on a polymorph (th-Al2O3). During the ALE cycle, a 7 s dose of HF was followed by a 20 s Ar purge.
A fluorinated surface was then generated. For each oxide dianion removed, two halide monoanions were added. These were then used to carry out halide-exchange reactions with the fluorinated aluminium oxide surface.
Process temperatures ranged from 150 degC to 400 degC. Higher process temperatures resulted in increased AlF3 and decreased Al-O bonds. Several atomic-scale models were optimized under periodic boundary conditions.
An EPC (Etch Product Concentration) value was calculated for different Ar purge times. It was found that higher process temperatures and pressures resulted in higher EPC values. However, at 200 degC, process pressure had no effect.
To determine the effect of ALEt process temperature on the Al2O3 film, the fluorinated surface was etched at four different temperatures. This was done using an etchant of 15 g of ammonium fluoride in glacial acetic acid. In a polypropylene beaker, the solution was soaked in for a specified period of time. After soaking, the wafer was rinsed with deionized water.
After the HF exposure, the Al 2p spectra are shown in Fig. 8. The peak intensity is slightly higher after the second ALE cycle.