Rare-Earth Scandate/TiN Gate Stacks in SOI MOSFETs Fabricated With a Full Replacement Gate Process

Terbium scandate (TbScO3) and lanthanum scan date (LaScO₃) have been investigated as gate dielectrics for metal-oxide-semiconductor field-effect transistors on both silicon-on-insulator (SOI) and strained SOI (sSOI) substrates. X-ray photoelectron spectroscopy analysis revealed the presence of a silicate at the interface for TbScO³ on Si, whereas a silicate/SiO₂-like interface was found for the LaScO₃ on Si. A full replacement gate process was developed to fabricate high-κ/metal gate fully depleted transistors on SOI and sSOI. LaScO₃ transistors with a gate length of 2 μm show excellent characteristics with steep subthreshold slopes of 72 mV/dec, high I_on/I_off ratios, and electron mobility of 180 cm²/V · s for SOI and 375 cm²/V · s for sSOI at low field, which is superior to corresponding TbScO₃ de vices. All sSOI transistors showed 2 times higher electron mobility than SOI reference devices.