Radiation Effects on Emerging Electronic Materials and Devices

1. June 13/14, 2006 Radiation Effects on Emerging Electronic Materials and Devices Radiation Effects in Emerging Materials Overview Leonard C. Feldman Vanderbilt University Department of Physics and Astronomy Vanderbilt Institute on Nanoscale Science and Engineering

2. Gate oxide Si metal MOS Schematic Radiation damage in emerging materials + + - - Other emerging materials i. Strained silicon ii. SOI iii. SiGe + + - - + + Characterization: i. Electrical: CV - Net charge Photo-CV - Deep and slow states I-V - Breakdown ii. Optical: Femto-second Pump-probe spectroscopy - alternate approach to charge quantification iii. Atomic level spectroscopy: Conductive tip AFM - identification of isolated leakage spots X-ray absorption - defect selective Gate Dielectrics i. High-k on Si: HfO2/Si, HfSiO/Si - (w and w/o interlayer) ii. High-k on Ge: HfDyO2/Ge iii. SiO2/Silicon carbide MURI review June’06

3. Goals The goals of this segment of the program are to identify and associate: i) radiation induced electrical defects with particular physical (atomic and electronic) configurations ii) to identify and elucidate new defects/traps that exist in emerging materials Requires a strong coupling to theory Requires strong coupling to sophisticated electrical New materials also give new insights that feed-back to the traditional structures

4. In situ photovoltage measurements using femtosecond pump-probe photoelectron spectroscopy and its application to metal-HfO2-Si structures Richard Haight IBM Measures band-bending in an in-situ configuration, without metal gate, yielding intrinsic electronic structure

5. Harmonic photon Laser field HARMONIC LASER PHOTOEMISSION High Harmonic Generation Ar jet Photon energies from 15-60 eV 800 nm ~35fs grating parabolic mirror TOF detector e e Pump, 800 nm, ~35fs sample High KE Main Chamber

6. p-FET p+ p+ n-type gate oxide channel Metal Gate for high-K MOS? For ideal p-FET at VG= 0 Vacuum level Interface Fermi Level (EIFL) j Sze: Phys. Semi. Dev. cSi But 1) Metal gate shows a similar problem EIFL  Midgap 2) In addition, Vt instability: charge trap? EF N-silicon High WF Metal HfO2 After anneal Goal: Understand the effect of thermal processes on high-K oxide & oxide-metal interface which affect MOS properties

7. Advanced Gate Stacks and Substrate Engineering Eric Garfunkel, Rutgers University External interactions: • Rich Haight, Supratik Guha – IBM • Gennadi Bersuker – Sematech • M. Green - NIST • E. Gusev - Qualcomm • W. Tsai - Intel • J. Chambers - TI

8. Rutgers CMOS Materials Analysis Use high resolution physical and chemical methods to examine new materials for radiation induced effects and compare with Si/SiO2/poly-Si stacks • Scanning probe microscopy – topography, surface damage, electrical defects • Ion scattering: RBS, MEIS, NRA, ERD – composition, crystallinity, depth profiles, H/D • Direct, inverse and internal photoemission – electronic structure, band alignment, defects • FTIR, XRD, TEM • Electrical – IV, CV • Growth – ALD, CVD, PVD

9. E0 = 1.4 MeV 4He E1 = KE0 RBS & CV of HfSiO/SiO2/p-Si films Electrical characterization Physical characterization Total dielectric thickness from RBS: ~10 to 11 nm Total dielectric thickness from CV: ~12 nm

10. Electron Traps in Hf-based Gate Stacks G. Bersuker, C. Young, P. Lysaght, R. Choi, M. Quevedo-Lopez, P. Kirsch, B. H. Lee SEMATECH

11. Electron Trap Depth profile • Factors affecting conversion of frequency to distance: • Capture cross sections decrease exponentially with depth • Recombination rate is limited by the capture of holes

12. Electron Trap Profile in High-k Layers • Electron traps uniformly distributed across the high-k film thickness • No significant difference in trap density between deposition methods and anneal ambients

13. Differences Between the Trapping States in x-ray and -Ray Irradiated Nano-crystalline HfO2, and Non-crystalline Hf Silicates G. Lucovsky, S. Lee, H. Seo, R.D. Schrimpf, D.M. Fleetwood, J. Felix, J. Luning,, L.B. Fleming, M. Ulrich, and D.E. Aspnes • Aim: The correlation of electronically active defects in alternate dielectrics with spectroscopic/electronic details extracted primarily via (soft) x-ray spectroscopies. • Processing defects which act as traps for radiation generated carriers • Defects created by the radiation itself.

15. G. Lucovsky NCSU Electronic Structure

16. spectroscopic studies of band edge electronic structure band edge defects - trapping asymmetry n-type Si substrates EOT~7 nm IMEC group/NCSU defects: ZrO2 (PC): TiO2 (SXPS) e-traps ~ 0.5 eV below HfO2 CB h-traps ~ 3 eV above HfO2 VB

17. Damage fundamentals: SiO2 vs HfO2 HfO2 =CAP HfO2 =CAP X-ray mass attenuation coefficient Proton stopping power For same capacitance ---- ~6 times more thickness

18. Silicon Carbide Collaboration Vanderbilt: Sriram Dixit, Sarit Dhar, S.T. Pantelides, John Rozen Auburn: J. Williams and group Purdue: J. Cooper and group

19. Silicon Carbide and SiC/SiO2 Interfaces • Silicon carbide as a radiation damage resistant material • High temp, high power applications • SiC-based neutron, charged particle detectors with improved radiation resistance • Materials improvements at all levels in recent years SiC/SiO2(N) Interfaces i) “Reveals” new, SiO2 radiation induced defects that fall within the SiC band-gap—4H, 6H, 3C, Si—a form of spectroscopy

20. SiC Power MOSFET Source (VSD) SiO2 Gate C - C Bonds SiO2 Si - Si Bonds N+ Substrate N+ Substrate Transition Layer Dangling Bonds Surface Roughness Due to P-Type Implant Anneal SiC SiO2 N+ SiC P base Oxide N+ Source Implanted P-Well MOSFET Channel Resistance N- drift region SiC N- Drift Region ISD Drain R = Rchan + Rintrinsic Rchan ~(mobility)-1

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22. Antibonding orbital Conduction bands Ec sp3 hybrid sp3 hybrid Ev Valence bands Bonding orbital

23. Logistics & MURI Collaborations Samples, Processes, Devices Rutgers, Sematech, NCSU Materials & Interface Analysis Rutgers, NCSU and IBM Theory Vanderbilt Radiation Exposure Vanderbilt Post-radiation Characterization Vanderbilt, Sematech, NCSU, Rutgers and IBM

24. Plans • Generation broader range of films and devices with high-K dielectrics (HfO2) and metal gate electrodes (Al, Ru, Pt). • Interface engineering: SiOxNy (vary thickness and composition) • Expand physical measurements of defects created by high energy photons and ions using SPM and TEM, in correlation with electrical methods. • Develop quantitative understanding of behavior as a function of particle, fluence, energy • Monitor H/D concentration and profiles, and effects on defect generation (by radiation) and passivation. • Determine if radiation induced behavior changes with new channel materials (e.g., Ge, InGaAs), strain, or SOI • Explore effects of processing and growth on radiation behavior. • Correlate with first principles theory.

25. 10:40 Overview: Radiation Effects in Emerging Materials Leonard Feldman, Vanderbilt University 11:00 Radiation Damage in SiO2/SiC Interfaces Sriram Dixit, Vanderbilt University 11:20 Spectroscopic Identification of Defects in Alternative Dielectrics Gerry Lucovsky, North Carolina State University 12:00 Lunch – Room 106 1:00 Radiation Effects in Advanced Gate Stacks Eric Garfunkel, Rutgers University G. Bersuker, SEMATECH

27. SiO2/SiC RBS/CH SiO2 “No” carbon

28. Interface State Density-----6H-4H Polytypes

29. Results • Generated thin films with high-K dielectrics (HfO2) and metal gate electrodes (Al, Ru). • Performed ion scattering, photoemission, internal photoemissions and inverse photoemission….on selected systems. • Had samples irradiated by Vanderbilt group (Feldman) • Performed SPM measurements of defects on selected systems