AVS 53rd International Symposium
    Electronic Materials and Processing Friday Sessions
       Session EM+TF-FrM

Paper EM+TF-FrM2
Process-Dependent Interface States at Mo/Hafnium Oxide/Si Interfaces

Friday, November 17, 2006, 8:20 am, Room 2003

Session: High-k Dielectric & Multi-Functional Oxide Growth & Processing
Presenter: S. Walsh, The Ohio State University
Authors: S. Walsh, The Ohio State University
L. Fang, The Ohio State University
J.K. Schaeffer, Freescale Semiconductor, Inc.
E. Weisbrod, Freescale Semiconductor, Inc.
L.J. Brillson, The Ohio State University
Correspondent: Click to Email
A major challenge for Hafnium Oxide (HFO) and other high-K dielectric materials is the control of their interface state and trapped charge densities. Among the chief electronic and chemical requirements for their development is the identification of post-growth processes to optimize oxide bonding within the thin dielectric films and at their interfaces. This requires characterization techniques that are nondestructive, that can measure electrically-active defects that correlate with electrical device features, and that can spatially isolate these defects within ultra-thin films to help identify their physical origins. We have used low energy electron-excited nanoscale-depth-resolved (DRCLS) spectroscopy to probe the bulk and interface defect states of ultra-thin Mo/HFO/Si with 8 different process sequences. After atomic layer deposition (ALD) of 4 nm HfO@sub 2@ on Si and an O@sub 2@ post treatment, we deposited 10 nm Mo using either plasma vapor or electron beam deposition, with or without a subsequent 1000@super O@C N@sub 2@ anneal, and with or without a forming gas anneal. DRCLS revealed pronounced gap state emissions within the ultrathin films and their interfaces with Mo and Si. There are multiple deep level emissions below the 5.5 eV band gap, including 3 peak emissions at 3.4, 3.5 eV, and 3.9-4.3 eV that can be associated with HFO oxygen vacancies in different charge states predicted theoretically.[1] In addition, states at 2 -2.6 eV that resemble known SiO@sub 2@-related nonbonding oxygen hole centers (NBOHC) and E' (positively charged O vacancy) native defects increase with depth within the 4 nm HFO film suggesting the formation of a Hf silicate at the HFO/Si interface. Furthermore, different process steps produce large changes in these states and for at least one sequence, a dramatic decrease in both types of defects. The differences between process sequences can be understood in terms of known reactions at HFO-Si interfaces.