| AVS 59th Annual International Symposium and Exhibition | |
| Nanomanufacturing Science and Technology Focus Topic | Monday Sessions |
| Session NM+NS+MS+EM-MoA |
| Session: | ALD and Scalable Processes for Nanomanufacturing |
| Presenter: | M.B. Mousa, North Carolina State University |
| Authors: | M.B. Mousa, North Carolina State University D.H. Kim, North Carolina State University C.J. Oldham, North Carolina State University G.N. Parsons, North Carolina State University |
| Correspondent: | Click to Email |
Atomic layer deposition (ALD) is used for nanoscale coatings with high uniformity and precise thickness control. Currently, most commercial ALD processes operate in batch mode. Expanding to ambient pressure can increase throughput and facilitate its integration for applications such as smart textiles, flexible electronics and synthetic polymer coatings. We find that under certain flow conditions in the trimethylaluminum (TMA)/water ALD process for Al2O3, increasing the reactor pressure from ~ 2 Torr to 760 Torr can produce excess film growth per cycle.
For this work, we studied ALD of Al2O3 using TMA/O3 and compared growth at ~ 2 Torr to that at 760 Torr in a flow tube reactor. We measured film thickness by ellipsometry and surface morphology by AFM. Also, we plan to monitor in-situ growth using a quartz crystal microbalance (QCM). At 2 Torr, by changing the ozone and TMA exposure times, we saw clear ALD saturation at ~ 0.45 Å/cycle at 170°C. A shorter purging time after the ozone exposure tends to increase the growth per cycle. Deposition at higher pressure results in growth rates between ~0.3 and 0.6 Å/cycle at 205°C, with lower growth rates obtained under higher gas flow rate conditions. For both the water and O3 processes at 760 Torr, a low gas flow rate of 0.5 standard liters per minute (slm) in our flow-tube reactor leads to a high growth rates of ~3 Å/cycle (for water) and 0.6 Å/cycle (for O3). For the water process at 760 Torr, increasing the flow rate to 10 slm somewhat decreases the growth per cycle to ~1.35 Å /cycle. However, for the O3 processes at 760 Torr, we need only a relatively small increase to 1.5 slm to achieve growth of 0.3 Å/cycle. This could be due to enhanced ozone desorption kinetics compared to the rate of water desorption under the conditions used. Also interestingly, we find for the water process that films deposited at high pressure have higher surface roughness than films deposited at low pressure. These results will help to identify the key parameters for new continuous atmospheric pressure ALD reactors designs.