Plasma-enhanced atomic layer deposition of zinc phosphate

• Zinc phosphate thin films were grown by plasma-enhanced atomic layer deposition.
• The process was characterized by in-situ spectroscopic ellipsometry, SEM/EDX, XPS, AFM, and XRD.
• The deposited material is a phosphorus-rich type of zinc phosphate glass.

Zinc phosphate thin films were grown by plasma-enhanced atomic layer deposition (ALD) using a sequence of trimethyl phosphate (TMP, Me3PO4) plasma, O2 plasma, and diethylzinc (DEZn, Et2Zn) exposures. The film growth was monitored by in-situ spectroscopic ellipsometry. At a substrate temperature of 300 °C, linear and saturated growth was observed with a remarkably high growth rate of 0.92 nm/cycle. As-deposited films were smooth, amorphous and very hygroscopic, suggesting a phosphorus-rich composition resembling zinc phosphate glass. Upon annealing in air, crystalline zinc phosphate and pyrophosphate phases were formed.