title: Interface Engineering for Atomic Layer Deposited Alumina Gate Dielectric on SiGe Substrates.
abstract: Optimization of the interface between high-k dielectrics and SiGe substrates is a challenging topic due to the complexity arising from the coexistence of Si and Ge interfacial oxides. Defective high-k/SiGe interfaces limit future applications of SiGe as a channel material for electronic devices. In this paper, we identify the surface layer structure of as-received SiGe and Al2O3/SiGe structures based on soft and hard X-ray photoelectron spectroscopy. As-received SiGe substrates have native SiOx/GeOx surface layers, where the GeOx-rich layer is beneath a SiOx-rich surface. Silicon oxide regrows on the SiGe surface during Al2O3 atomic layer deposition, and both SiOx and GeOx regrow during forming gas anneal in the presence of a Pt gate metal. The resulting mixed SiOx-GeOx interface layer causes large interface trap densities (Dit) due to distorted Ge-O bonds across the interface. In contrast, we observe that oxygen-scavenging Al top gates decompose the underlying SiOx/GeOx, in a selective fashion, leaving an ultrathin SiOx interfacial layer that exhibits dramatically reduced Dit.
authors.affiliation: Department of Electrical Engineering, Stanford University , Stanford, California 94305, United States.
authors.forename: Liangliang
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Engineering Department, Cambridge University , Cambridge CB2 1PZ, United Kingdom.
authors.forename: Yuzheng
authors.initials: Y
authors.lastname: Guo
authors.affiliation: Applied Materials , Santa Clara, California 95054, United States.
authors.forename: Vinayak Vishwanath
authors.initials: VV
authors.lastname: Hassan
authors.affiliation: Department of Materials Science and Engineering, Stanford University , Stanford, California 94305, United States.
authors.forename: Kechao
authors.initials: K
authors.lastname: Tang
authors.affiliation: Applied Materials , Santa Clara, California 95054, United States.
authors.forename: Majeed A
authors.initials: MA
authors.lastname: Foad
authors.affiliation: Materials Science and Engineering Laboratory, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States.
authors.forename: Joseph C
authors.initials: JC
authors.lastname: Woicik
authors.affiliation: SLAC National Accelerator Center , Menlo Park, California 94025, United States.
authors.forename: Piero
authors.initials: P
authors.lastname: Pianetta
authors.affiliation: Engineering Department, Cambridge University , Cambridge CB2 1PZ, United Kingdom.
authors.forename: John
authors.initials: J
authors.lastname: Robertson
authors.affiliation: Department of Materials Science and Engineering, Stanford University , Stanford, California 94305, United States.
authors.forename: Paul C
authors.initials: PC
authors.lastname: McIntyre
keywords: Al2O3; MOSCAP; SiGe; atomic layer deposition; high-k; interface traps