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

Gate oxide Si metal MOS Schematic 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 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

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

In situ photovoltage measurements using femtosecond pump-probe photoelectron spectroscopy and its application to metal-HfO 2 -Si structuresIn situ photovoltage measurements using femtosecond pump-probe photoelectron spectroscopy and its application to metal-HfO 2 -Si structures Richard Haight IBM Measures band-bending in an in-situ configuration, without metal gate, yielding intrinsic electronic structure

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

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

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

Rutgers CMOS Materials Analysis 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 Use high resolution physical and chemical methods to examine new materials for radiation induced effects and compare with Si/SiO 2 /poly-Si stacks

Total dielectric thickness from RBS: ~10 to 11 nm RBS & CV of HfSiO/SiO 2 /p-Si films Physical characterization Electrical characterization Total dielectric thickness from CV: ~12 nm E 0 = 1.4 MeV 4 He E 1 = KE 0

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

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

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

Differences Between the Trapping States in x-ray and  - Ray Irradiated Nano-crystalline HfO 2, 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. i)Processing defects which act as traps for radiation generated carriers ii)Defects created by the radiation itself.

G. Lucovsky NCSU Electronic Structure

spectroscopic studies of band edge electronic structure band edge defects - trapping asymmetry n-type Si substrates EOT~7 nm IMEC group/NCSU e-traps ~ 0.5 eV below HfO 2 CB h-traps ~ 3 eV above HfO 2 VB defects: ZrO 2 (PC)  : TiO 2 (SXPS) 

Damage fundamentals: SiO 2 vs HfO 2 Proton stopping power X-ray mass attenuation coefficient For same capacitance ---- ~6 times more thickness HfO 2 =CAP

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

Silicon Carbide and SiC/SiO 2 Interfaces Silicon carbide as a radiation damage resistant material i)High temp, high power applications ii)SiC-based neutron, charged particle detectors with improved radiation resistance iii)Materials improvements at all levels in recent years SiC/SiO 2 (N) Interfaces i) “Reveals” new, SiO 2 radiation induced defects that fall within the SiC band-gap—4H, 6H, 3C, Si—a form of spectroscopy

N+ Source Implanted P-Well N- Drift Region Oxide SiO 2 Surface Roughness Due to P-Type Implant Anneal SiC MOSFET Channel Resistance Transition Layer SiC SiO 2 Dangling Bonds Si - Si Bonds C - C Bonds SiC Power MOSFET N+ Substrate Gate Source (V SD ) N+ P base Drain N- drift region SiO 2 SiC I SD R = R chan + R intrinsic R chan ~ (mobility) -1

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EvEv EcEc sp 3 hybrid Bonding orbital Antibonding orbital Valence bands Conduction bands

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

Plans Generation broader range of films and devices with high-K dielectrics (HfO 2 ) and metal gate electrodes (Al, Ru, Pt). Interface engineering: SiO x N y (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.

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

RBS/CH SiO 2 “No” carbon SiO 2 /SiC

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

Results Generated thin films with high-K dielectrics (HfO 2 ) 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