Band offsets of atomic layer deposited Al2O3 and HfO2 on Si measured by linear and nonlinear internal photoemission

Abstract

AbstractWe present measurements of band alignment of atomic layer deposited high‐k dielectrics on Si(100) using linear internal photoemission (IPE), detected by measuring photocurrent from a biased MOS capacitor, and internal multi‐photon photoemission (IMPE), detected by optical second‐harmonic generation (SHG). In IPE, Band offsets are extracted from either the threshold of quantum yield; in IMPE, they are determined by detecting discrete increments in multi‐photon order. IPE and IMPE yielded identical conduction band (CB) offsets (2.0 eV) for as‐deposited Si/Al2O3 structures with 10 and 3 nm oxides, respectively, in excellent agreement with previous measurements of annealed structures. Band offset measurements for Si/HfO2, on the other hand, show a strong (0.3 eV) upshift of the oxide valence band (VB) maximum, and an equal decrease of the oxide band gap upon post‐deposition annealing (PDA) at 600 °C, while the CB offset remains unchanged. We attribute the shift of the VB edge to thermally driven oxygen diffusion away from the Si/HfO2 interface.