High-permittivity YScO3 thin films by atomic layer deposition using two precursor approaches

Amorphous YScO3 thin films have been deposited by atomic layer deposition using two types of volatile metal precursors, viz. beta-diketonate-type metal complexes M(thd)(3) (M = Y, Sc; thd = 2,2,6,6-tetramethyl-3,5-heptanedionato) and organometallic cyclopentadienyl compounds tris(methylcyclopentadienyl)yttrium (C5H4CH3)(3)Y and tris(cyclopentadienyl)scandium Cp3Sc (Cp = C5H5). Ozone and water were used as oxygen sources in the M(thd)(3) and cyclopentadienyl precursor-based processes, respectively. Deposition temperatures were 335-350 degrees C for the M(thd)(3) precursor-based process and 300 degrees C for the cyclopentadienyl precursor-based process. Metal ratio and film thickness were easily controlled by varying the metal precursor pulsing ratio and the number of deposition cycles. Stoichiometric YScO3 films contained less than 1 atom% hydrogen and less than 0.2 atom% carbon regardless of the precursors used. The as-deposited stoichiometric films were smooth, amorphous and they had high permittivity (14-16). Films deposited using the cyclopentadienyl precursor-based process started to crystallize at 800 degrees C while films deposited using the M(thd)(3) precursor-based process still remained amorphous at this temperature. Films deposited using the latter process crystallized at 1000 degrees C. Crystallization significantly deteriorated the dielectric properties of the films, however.