Organic grafting on Si for interfacial SiO₂ growth inhibition during chemical vapor deposition of HfO₂

Engineering of the silicon/high-permittivity (high-κ) dielectric interface by grafting an ultrathin organic layer on the silicon surface before HfO₂ deposition is explored. Si(111) and Si(100) surfaces are functionalized using methyl groups as well as long alkoxy and functionalized alkyl chains. Amorphous HfO₂ films are deposited by metal organic chemical vapor deposition. We show that methyl or carboxydecyl groups efficiently inhibit the formation of SiO₂, while the quality of the HfO₂ layer (uniformity, permittivity) is not affected by the grafting. The flatband voltage in metal-oxide-semiconductor structures with films grown on methyl-grafted p-type Si(100) is shifted by an additional ∼100 to 300 mV compared to that with films grown on a chemical SiO₂ oxide. This is in good agreement with the expected dipole effect related to the grafting of such molecules on silicon. The interfacial state density is comparable to the one measured on films grown on SiO₂/Si. This study opens up the route for the engineering of the Si/high-κ oxide interface using organic grafting.