Atomic Layer Deposition of Aluminum and Titanium Phosphates

The atomic layer deposition (ALD) of phosphate containing thin films using reactions between the metal halide and the phosphorus source without any additional oxygen sources was examined. Two very common metal halides, AlCl3 and TiCl4, were used in conjunction with trimethyl phosphate (TMPO) to grow corresponding metal phosphate films. Aluminum phosphate thin films were deposited at temperatures between 150 and 400 degrees C while titanium phosphate films grew between 275 and 450 degrees C. Amorphous films of Al2.6PO7.0 and Al1.6PO5.6 were deposited at 200 and 300 degrees C, respectively, while the amorphous titanium phosphate films deposited at 300 and 400 degrees C consisted of Ti0.8PO3.9 and Ti0.6PO3.5 (Ti1.2P2O7). The stability and crystallization of the films were studied with high temperature XRD, while the surface morphology of the annealed films was studied using FESEM.