Atomic Layer Deposition of Aluminum and Titanium Phosphates

The atomic layer deposition (ALD) of phosphate containing thin films using reactions between metal halide and 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 °C while titanium phosphate films grew between 275 and 450 °C. Amorphous films of Al_2.6PO_7.0 and Al_1.6PO_5.6 were deposited at 200 and 300 °C, respectively, while the amorphous titanium phosphate films deposited at 300 and 400 °C consisted of Ti_0.8PO_3.9 and Ti_0.6PO_3.5 (Ti_1.2P₂O₇). The films were analyzed using high temperature XRD to study the crystallization and stability of the deposited films. Also the surface morphology of the annealed films was examined by FESEM.