Electrical Properties of CeO_2/La_2O_3 Stacked Gate Dielectrics Fabricated by Chemical Vapor Deposition and Atomic Layer Deposition

摘要

Stacked gate dielectrics composed of CeO_2 and La_2O_3 were fabricated on Si substrates and their structures and electrical properties were investigated. Two types of stacked structures were compared: CeO_2 grown on La_2O_3 (La_2O_3/CeO_2) and La_2O_3 grown on CeO_2 (CeO_2/La_2O_3). The La_2O_3 and CeO_2 layers were formed by atomic layer deposition (ALD) and chemical vapor deposition (CVD), respectively. The La_2O_3/CeO_2 structure showed a larger equivalent oxide thickness (EOT) than the CeO_2/La_2O_3 structure due to the silicate formation of the CeO_2 layer in contact with Si. Metal-oxide-semiconductor field-effect transistors (MOSFETs) and capacitors constructed with the La_2O_3/CeO_2 structure showed threshold and flat-band voltages close to the ideal ones. Effective channel mobilities for the MOSFETs were compared among three structures: single-layer La_2O_3, La_2O_3/CeO_2, and CeO_2/La_2O_3. EOT scaling was achieved without degrading the mobility of the CeO_2/La_2O_3 structure, which reproduced previous results for the same structure formed by the electron-beam evaporation technique. The gate-leakage characteristics for the CVD/ALD samples were also investigated.