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

Abstract

Amorphous YScO₃ thin films have been deposited by atomic layer deposition using two types of volatile metal precursors, viz. β-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)₃Y 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 °C for the M(thd)₃ precursor-based process and 300 °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 °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 °C. Crystallization significantly deteriorated the dielectric properties of the films, however.