MRS Spring Meeting 2006
Conference paper

A comparison of electrical and physical properties of MOCVD hafnium silicate thin films deposited using various silicon precursors

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We report on the impact of silicon precursor choice on the electrical and physical properties of hafnium silicate (HfSiO) gate dielectrics deposited by metalorganic chemical vapor deposition (MOCVD). Hafnium tert-butoxide (HTB) was used as the hafnium source and silane and tetraethylorthosilicate (TEOS) were used as silicon sources. Elemental depth profiles were measured with sub-nm resolution using medium energy ion scattering (MEIS). For Hf-rich films employing TEOS as the silicon precursor, relatively little Si is incorporated at the bottom interface compared with the top; while using SiH4, a more uniform Si distribution is achieved. These physical differences are then correlated with the electrical performance of transistors employing polysilicon gate electrodes. Transistors incorporating SiH4 based HfSiO x gate dielectrics with low silicon concentrations have lower C-V hysteresis and higher high field mobility than those using TEOS based dielectrics, We demonstrate polysilicon gated transistors which have an electrical thickness in inversion (Tinv) that can be scaled to ∼21 A with good leakage reduction when employing nitrided bottom interface layers in combination with optimized HfSiOx dielectrics. Reduced silicon concentration resulted in a lower inversion thickness for a fixed physical thickness contributing to the higher drive currents in transistors. © 2006 Materials Research Society.