Effect of Deuterium Ion Implantation Dose on Microstructure and Nanomechanical Properties of Silicon

Implantation of hydrogen into silicon with subsequent annealing (Smart-Cut Technology) is applied to produce microelectronic devices. Improved characteristics of the resulting structures were achieved by using implantation of deuterium instead of hydrogen. The nanoindentation technique is widely used to measure the hardness H and elasticity modulus E of materials at the nanoscale. The aim of the present work is to investigate the influence of deuterium ion implantation dose on the structure and mechanical properties of single crystal silicon at the nanoscale. The influence of the deuterium ion implantation with an implantation dose ranging from 2×1015 to 1×1018 D/cm2 on the structure and mechanical properties of single crystal silicon at the nanoscale has been investigated. Polished (111) silicon samples were implanted at 293 K by using a deuterium ion beam with an ion energy of 24 keV. It was shown by Raman spectroscopy that, depending on the implantation dose, three structural states are formed in silicon: a solid solution of deuterium (D) in Si, a solid solution mixed with the Si amorphous phase, and an amorphous state (a-Si:D) only. Thermal desorption (TD) spectroscopy shows that at low implantation doses, the deuterium TD spectra exhibit a single peak with a maximum at Tmax ~ 575 K. At doses above 5×1017 D/cm2, a lowtemperature peak with a maximum at 500 K appears that is indicative of the formation of amorphous hydrogenated silicon a-Si:D. Nanoindentation tests have shown that in the regime of full plasticity in the indenter contact region ( 100 nm), the formation of deuterium solid solution in Si causes an increase in the sample surface hardness up to 14.1 GPa. The surface hardness sharply decreased down to 3.6 GPa with the a-Si:D layer formation.