(Invited) Atomic Layer Deposition for Epitaxial Oxides on Silicon

Abstract

Thin films of crystalline oxides integrated with silicon are of interest for novel devices that utilize the rich variety of functional properties of oxide materials. Growth of crystalline oxides on silicon requires careful control of a nanometer thin transition region to avoid deleterious side reactions such as oxidation of the substrate. Submonolayer surface reconstructions of alkaline earth metals such as Sr are key to controlling the interface for successful growth. Previously, this has only been accomplished using molecular beam epitaxy growth methods, but there is interest to create an alternative process based on atomic layer deposition. In this work we demonstrate the successful deposition of the critical (2x1) Sr/Si reconstruction using SrO ALD deposition combined with oxide desorption. The results show that ALD based crystalline oxide heteroepitaxy is promising.

Positive and negative dipole layer formation at high-k/SiO2 interfaces simulated by classical molecular dynamics

“…The silicate layers at the MgO=SiO 2 and SrO=SiO 2 interfaces are about twice as thick as that of the Al 2 O 3 =SiO 2 interface. This result agrees well with the experimental results of other studies, wherein MgO and SrO are reported to form a silicate layer at the interface with SiO 2 , 30,31) whereas the silicate layer is barely formed at the Al 2 O 3 =SiO 2 interface. 32,33) In order to clarify the ion species that contributes most to the electric dipole, we calculated the charge migration moment (CMM) for each species.…”

Driving force of oxygen-ion migration across high-k/SiO2 interface

“…In these cases, the dipole layer is induced by the migration of metal cations (Mg + , Sr + ) from the high-k oxide side to the SiO 2 side, and a silicate layer is formed at these interfaces. The silicate-layer formation has been observed experimentally at MgO=SiO 2 and SrO= SiO 2 interfaces 20,21) but not at Al 2 O 3 =SiO 2 interfaces. 22,23) These results indicate that the negative V FB shift is induced in the course of the formation of stable silicate phases.…”

(Invited) Molecular Dynamics of Dipole Layer Formation at High-k/SiO2Interface

“…The silicate layer is the compositional transition layer at the interface, which is defined as the interval between the point at which the Si density becomes 90% of the bulk SiO 2 , and the point at which the density of the high-k metal ion becomes 90% of the bulk value. The silicate layers at the MgO/SiO In the previous experimental studies, MgO and SrO are reported to form a silicate layer at the interface with SiO 2 , [26,27], whereas the silicate layer is barely formed at the Al 2 O 3 /SiO 2 interface. [28,29]…”