Nanomechanical study of amorphous and polycrystalline ALD HfO_{2 thin films

Thin films of hafnium oxide (HfO2) were deposited by atomic layer deposition (ALD). The structural properties of the deposited films were characterised by transmission electron microscopy (TEM) and X-ray diffraction (XRD). We investigated the effect of phase transformations induced by thermal treatments on the mechanical properties of ALD HfO2 using nanoindentation. The elastic modulus of the amorphous low temperature deposited ALD HfO2 films was measured to be 370 ± 20 GPa. Subsequent to crystallisation by annealing in a rapid thermal annealing (RTA) chamber, the elastic modulus dropped to 240 ± 20 GPa. Similarly, the Meyer hardness decreased from a value of 18 ± 1 GPa for amorphous HfO2 to 15 ± 1 GPa following the transition temperature from amorphous to polycrystalline HfO2.