Advanced Gate Stacks and Substrate Engineering Eric Garfunkel and Evgeni Gusev Rutgers University

1. Advanced Gate Stacks and Substrate Engineering Eric Garfunkel and Evgeni Gusev Rutgers University Departments of Chemistry and Physics Institute for Advanced Materials and Devices Piscataway, NJ 08854 Rutgers

2. Gate Stack Gate dielectric approaching a fundamental limit (a few atomic layers) Advanced Gate Stack Materials • Motivation: Severe power dissipation in aggressively scaled conventional SiO2 gate oxides Rutgers

3. High-κ Dielectric Metal Electrode Barrier? SiO2 Monolayer? 10-30nm Source Drain SiGe? CMOS transistor ~2008? Goal: develop understanding of interaction of radiation with CMOS materials C  Ae/d EOT - effective oxide thickness • New materials: metal electrodes, high-K dielectrics, substrates • Electronic structure, defects, band alignment Rutgers

4. Advanced Gate Stack: Materials Challenges • Enormous materials/interface • challenge • rad. response not fully understood Rutgers

5. ? Oxide thermal stability: Si + MxOy M + SiO2 Si + MxOy MSiz + SiO2 (or silicate) G>0 @1000°K ? ? ? ? ? ? ? ? ? ? ? ? ? ? Selected material requirements for high-K dielectric + metal electrode CMOS gate stack • High-K dielectric • high thermal stability; no reaction with substrate or metal • high uniformity: minimal roughness, single amorphous phase preferred • low electrical defect concentration • high permittivity • Metal gate electrode • Appropriate band alignment wrt substrate semiconductor and dielectric • high thermal stability; no reaction with dielectric • high conductivity Rutgers

6. Rutgers CMOS Materials Analysis Capabilities • Ion scattering: RBS, MEIS, NRA, ERD – composition, crystallinity, depth profiles, H/D • Direct, inverse and internal photoemission – electronic structure, band alignment, defects • Scanning probe microscopy – topography, surface damage, electrical defects, capacitance • FTIR, XRD, TEM, STEM • Electrical – IV, CV • Growth – ALD, MOCVD, PVD Rutgers

7. 2 1 3 Cl 0 N2 flow Cl Hf Cl HCl Cl HCl Cl Cl Cl Cl Cl Cl Cl Cl Cl Cl Cl Hf Hf Hf Hf Hf Cl Cl Hf Hf Si Si Si Si Si Si Si Si Si Si Si Si Chemisorption of HfCl4 Inert gas purge Chemisorption of H2O Starting surface 4 Hf Hf Hf Silicon Substrate Silicon Substrate Si Si Si Inert gas purge Silicon Substrate Silicon Substrate Silicon Substrate Silicon Substrate Atomic Layer Deposition (ALD) Why Atomic Layer Deposition? • monolayer control of dielectric and metal film growth • mixed oxides and nanolaminates - allows tailored films • conformality advantage for novel structures • low temperature deposition ~ 300ºC Rutgers

8. Rutgers

9. ~100 keV p+ ZrO2 (ZrO2)x(SiO2)y Si(100) MEIS depth profiling depth profile • Sensitivity:  10+12 atoms/cm2 (Hf, Zr)  10+14 atoms/cm2 (C, N) • Accuracy for determining total amounts:  5% absolute (Hf, Zr, O),  2% relative  10% absolute (C, N) • Depth resolution: (need density)  3 Å near surface  8 Å at depth of 40 Å Rutgers

10. Isotope studies of diffusion and growth in metal/high-K gate stacks Isotope tracer studies 30Å Al2O3 annealed in 3 Torr 18O2 ZrO2 film re-oxidized in 18O2 Rutgers

11. a 18O 15N p Nuclear resonance methods for light element profiling Differential cross section Energy (keV) Schematic of ion beam-film reactions for (p,g), (p,a) and (p,ga) resonance reactions. Control incident energy to get depth information Rutgers

12. Some low energy nuclear resonances Rutgers

13. Deuterium distribution in SiO2 films Rutgers

14. EF Ec EF EV semiconductor metal high-k SiO2 Determine electronic structure and band alignment for metal/high-k/Si gate stack • Use high resolution spectroscopic tools to: • Determine band alignment and defects • Observe changes induced by radiation Rutgers

15. e- e- # of Photons e- e- e- Photon Energy e- Electron Energy CB Electron Counts EF VB Core Level Experimental tools to examine electronic structure Photoemission (Occupied States) Inverse Photoemission (Unoccupied States) EF EVBM CB ECBM EF EF VB CL Rutgers

16. Additional experimental tools I-V XAS, EELS (Core CB) Optical methods STM/C-AFM probe e- … Eg hw hw V V CB EF EF EF EF Eg Eg Eg VB Met Si Met Si Met Si CL High-k High-k High-k Rutgers

17. DEc = 1.15 eV DEg = 5.7 eV DEv = 3.40 eV SiO2 Si ZrO2 Photoemission and Inverse Photoemission of ZrO2/Si Theory Ä resolution First Principles Theory First Principles Theory • VBM, CBM Determination: • Comparison with Theory(where possible) • Extrapolation • Establish band offsets VBM = EF - 4.2 eV CBM = EF + 1.4 eV Rutgers

18. M/Ox a EF Ec EF b EV c metal semiconductor high-k Internal Photoemission (IntPES) Si/Ox Ec EF EF EV metal semiconductor high-k (a) Ec(Hik)-EF(met.) e-IntPES; (b) photo-excitation; optical band gap; (c) Ec(sc)-Ev (Hik) h-IntPES Chopper Probe station Arc lamp Monochromator I-V Source Measure Unit Lock-in amplifier Rutgers

19. W =3.8 eV Si =4.4 eV W SiO2 Si IntPES: W / SiO2 / n-Si Negative Bias on Si, Si/ SiO2 : ~4.4 eV Combine positive and negative bias data to determine W and Si barriers with SiO2 Rutgers

20. Conductive Tip AFM Image and I-V Behavior of a Ru/HfO2/Si Stack Image physical and spectroscopic behavior of radiation induced defects For simple F-N tunneling with an electron effective mass of 0.18, the HfO2/Si conduction band barrier height is 1.4eV Rutgers

21. I. High-mobility Channels: Germanium • Carrier mobility enhancement • “Interface-free” high-K Rutgers

22. II. High-mobility Channels: HfO2 on strained Si Rutgers

23. High-mobility Channels: HfO2 on strained Si • Significant mobility enhancement for HfO2 on strained Si Rutgers

24. III. High-mobility Channels: Si orientations • Hybrid (Si) Orientation Technology: combines best NFET performance for Si(100) and PFET for Si(110) PFET NFET Rutgers

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

26. Plans General goal: to examine new materials for radiation induced effects and compare with Si/SiO2/poly-Si stacks • Generation of films and devices with high-K dielectrics (HfO2) and/or metal gate electrodes (Al, Ru, Pt) with 1-50nm thickness • Interface engineering: SiOxNy (vary thickness and composition) • Physical measurements of defects: STM, AFM, TEM vs particle, fluence, energy • H/D concentration and profiles, and effects on defect generation and passivation • Correlate UHV-based studies with electrical and internal photoemission measurements. • Explore different processing and growth methods. • Correlate with first principles theory. • Develop predictive understanding of radiation induced effects Rutgers

27. Industrial contacts • Gusev, Guha - IBM • Liang, Tracy - Freescale • Tsai - Intel • Chambers, Columbo - TI • Vogel, Green - NIST • Gardner, Lysaght, Bersuker, Lee – Sematech • Edwards, Devine – AFOSR Rutgers