Zhao Mei

Effective interface passivation of a Ge/HfO2 gate stack using ozone pre-gate treatment and ozone ambient annealing

The physical and electrical properties of a Ge/GeO2/HfO2/Al gate stack are investigated. A thin interfacial GeO2 layer (~1 nm) is formed between Ge and HfO2 by dual ozone treatments, which passivates the Ge/high-k interface. Capacitors on p-type Ge substrates show very promising capacitance-voltage (C—V) characteristics by using in situ pre-gate ozone passivation and ozone ambient annealing after high-k deposition, indicating efficient passivation of the Ge/HfO2 interface. It is shown that the mid-gap interface state density atthe Ge/GeO2 interface is 6.4 × 1011 cm−2 eV−1. In addition, the gate leakage current density of the Ge/GeO2/HfO2/Al gate stack passivated by the dual ozone treatments is reduced by about three orders of magnitude compared to that of a Ge/HfO2/Al gate stack without interface passivation.

Fermi level depinning by a C-containing layer in a metal/Ge structure by using a chemical bath

Insertion of a C-containing layer in a metal/Ge structure, using a chemical bath, enabled the Schottky barrier height (SBH) to be modulated. Chemical baths with 1-octadecene, 1-hexadecene, 1-tetradecene, and 1-dodecene were used separately with Ge substrates. An ultrathin C-containing layer stops the penetration of free electron wave functions from the metal to the Ge. Metal-induced gap states are alleviated and the pinned Fermi level is released. The SBH is lowered to 0.17 eV. This new formation method is much less complex than traditional ones, and the result is very good.