Surface mechanical property assessment of ultra-thin HfO2 films

As the devices scale down, HfO2 is an excellent gate dielectric material and can replace SiO2 in complementary metal-oxide semiconductor technology. However, the mechanical property-based reliability such as wear resistance and deformation mechanism are rarely understood. This paper describes the effect of annealing treatment on 20-nm-thick HfO2 films under varying applied normal forces (31.3-104.2 mu N). According to grazing incident X-ray diffraction analysis, the HfO2 thin films changed from amorphous to polycrystalline structure after annealing treatment. The scratch depth relative to initial surface was proportional to normal force. In addition, plowing behavior dominated the deformation mechanism in the form of lumps along the edge of groove by atomic force microscopy images. The annealing-induced crystallization resulted in reduced penetration depth, coefficient of friction, and wear rate at all applied normal forces, indicating that the surface hardness and wear resistance of HfO2 thin films can be enhanced through appropriate annealing treatment. Furthermore, substrate effect caused negative correlation between wear resistance and normal force was not obvious to annealed samples. It could be attributed to the broadening of HfSixOy interfacial layer which enhanced the structure strength. (C) 2013 Elsevier B. V. All rights reserved.