Deposition of hafnium silicate films by liquid injection MOCVD using a single source or dual source approach

Abstract

Two approaches have been investigated for the MOCVD of high-κ hafnium silicate (HfSi_xO_y) films for gate dielectric applications. The first approach using the novel “single source” precursor [Hf(OSiBu^tMe₂)₄(Et₂NH)], gave a level of Si (∼10 at%) which showed little variation over a range of growth temperatures and oxygen partial pressures. The second, more flexible approach, uses two separate Hf and Si sources, Hf(NMe₂)₄ and Bu^tMe₂SiOH, and allows good control of the Si concentration in HfSi_xO_y, depending on the relative precursor ratios, up to a maximum level of 18 at%. The dielectric properties of the HfSi_xO_y films deposited by this method were shown to be very good. In the dual source process it is proposed that an intermediate containing direct Hf–OSiBu^tMe₂ bonds is formed in situ in the gas phase. The crystal structure of [Hf(OSiBu^tMe₂)₄(Et₂NH)] is also reported.