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MURI 1 Rutgers 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 Slide 2 MURI 2 Rutgers Advanced Gate Stack Materials u Motivation: Severe power dissipation in aggressively scaled conventional SiO 2 gate oxides Gate Stack Gate dielectric approaching a fundamental limit (a few atomic layers) Slide 3 MURI 3 Rutgers SiO 2 Monolayer? Metal Electrode High- Dielectric SourceDrain SiGe? Barrier? 10-30nm CMOS transistor ~2008? Goal: develop understanding of interaction of radiation with CMOS materials C A /d EOT - effective oxide thickness u New materials: metal electrodes, high-K dielectrics, substrates u Electronic structure, defects, band alignment Slide 4 MURI 4 Rutgers Advanced Gate Stack: Materials Challenges Enormous materials/interface challenge rad. response not fully understood Slide 5 MURI 5 Rutgers 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 ? ? ? ?????????? ? ? Oxide thermal stability: Si + M x O y M + SiO 2 Si + M x O y MSi z + SiO 2 (or silicate) G>0 @1000K Metal gate electrode Appropriate band alignment wrt substrate semiconductor and dielectric high thermal stability; no reaction with dielectric high conductivity Slide 6 MURI 6 Rutgers Rutgers CMOS Materials Analysis Capabilities u Ion scattering: RBS, MEIS, NRA, ERD composition, crystallinity, depth profiles, H/D u Direct, inverse and internal photoemission electronic structure, band alignment, defects u Scanning probe microscopy topography, surface damage, electrical defects, capacitance u FTIR, XRD, TEM, STEM u Electrical IV, CV u Growth ALD, MOCVD, PVD Slide 7 MURI 7 Rutgers Starting surface N 2 flow Si 0 Chemisorption of HfCl 4 1 Cl HfHf HfHf Chemisorption of H 2 O Si 3 Cl HfHf HCl HfHf HfHf Inert gas purge Si 4 HfHf HfHf HfHf Inert gas purge Si 2 Cl HfHf HfHf HfHf monolayer control of dielectric and metal film growth mixed oxides and nanolaminates - allows tailored films conformality advantage for novel structures low temperature deposition ~ 300C Why Atomic Layer Deposition? Silicon Substrate Silicon Substrate Silicon Substrate Silicon Substrate Silicon Substrate Silicon Substrate Atomic Layer Deposition (ALD) Slide 8 MURI 8 Rutgers Slide 9 MURI 9 Rutgers ZrO 2 (ZrO 2 ) x (SiO 2 ) y Si(100) ~100 keV p + depth profile MEIS depth profiling u Sensitivity: 10 +12 atoms/cm 2 (Hf, Zr) 10 +14 atoms/cm 2 (C, N) u Accuracy for determining total amounts: 5% absolute (Hf, Zr, O), 2% relative 10% absolute (C, N) u Depth resolution: (need density) 3 near surface 8 at depth of 40 Slide 10 MURI 10 Rutgers ZrO 2 film re-oxidized in 18 O 2 30 Al 2 O 3 annealed in 3 Torr 18 O 2 Isotope studies of diffusion and growth in metal/high-K gate stacks Isotope tracer studies Slide 11 MURI 11 Rutgers Nuclear resonance methods for light element profiling Schematic of ion beam-film reactions for (p, ), (p, ) and (p, ) resonance reactions. Control incident energy to get depth information 18 O 15 N p Energy (keV) Differential cross section Slide 12 MURI 12 Rutgers Some low energy nuclear resonances Slide 13 MURI 13 Rutgers Deuterium distribution in SiO 2 films Slide 14 MURI 14 Rutgers Determine electronic structure and band alignment for metal/high- /Si gate stack Use high resolution spectroscopic tools to: Determine band alignment and defects Observe changes induced by radiation EcEc EFEF EVEV metal semiconductor EFEF high- SiO 2 Slide 15 MURI 15 Rutgers Inverse Photoemission (Unoccupied States) e-e- e-e- Photoemission (Occupied States) e-e- e-e- e-e- e-e- Experimental tools to examine electronic structure EFEF CL VB CB EFEF VB Core Level CB Electron Counts Electron Energy E VBM Photon Energy # of Photons E CBM EFEF EFEF Slide 16 MURI 16 Rutgers e-e- Additional experimental tools EFEF VB CL CB XAS, EELS (Core CB) Optical methods EFEF EgEg EgEg MetSi High-k EFEF EgEg MetSi High-k V I-V EFEF EgEg MetSi High-k V probe STM/C-AFM Slide 17 MURI 17 Rutgers Photoemission and Inverse Photoemission of ZrO 2 /Si CBM = E F + 1.4 eV VBM = E F - 4.2 eV First Principles Theory Theory resolution First Principles Theory E c = 1.15 eV E v = 3.40 eV E g = 5.7 eV ZrO 2 SiO 2 Si VBM, CBM Determination: Comparison with Theory (where possible) Extrapolation Establish band offsets Slide 18 MURI 18 Rutgers Internal Photoemission (IntPES) EcEc EFEF EVEV M/Ox metalsemiconductor EFEF high- a c b EcEc EFEF EVEV Si/Ox metal semiconductor EFEF high- (a) E c (Hi )-E F (met.) e-IntPES; (b) photo-excitation; optical band gap; (c) E c (sc)-E v (Hi ) h-IntPES Arc lampMonochromator Chopper Lock-in amplifier I-V Source Measure Unit Probe station Slide 19 MURI 19 Rutgers IntPES: W / SiO 2 / n-Si Negative Bias on Si, Si/ SiO2 : ~4.4 eV Si =4.4 eV W =3.8 eV W SiO 2 Si Combine positive and negative bias data to determine W and Si barriers with SiO 2 Slide 20 MURI 20 Rutgers Conductive Tip AFM Image and I-V Behavior of a Ru/HfO 2 /Si Stack For simple F-N tunneling with an electron effective mass of 0.18, the HfO 2 /Si conduction band barrier height is 1.4eV Image physical and spectroscopic behavior of radiation induced defects Slide 21 MURI 21 Rutgers I. High-mobility Channels: Germanium u Carrier mobility enhancement u Interface-free high-K Slide 22 MURI 22 Rutgers II. High-mobility Channels: HfO 2 on strained Si Slide 23 MURI 23 Rutgers High-mobility Channels: HfO 2 on strained Si u Significant mobility enhancement for HfO2 on strained Si Slide 24 MURI 24 Rutgers III. High-mobility Channels: Si orientations u Hybrid (Si) Orientation Technology: combines best NFET performance for Si(100) and PFET for Si(110) PFET NFET Slide 25 MURI 25 Rutgers Logistics & MURI Collaborations Samples, Processes, Devices Rutgers, NCSU, IBM Materials & Interface Analysis Rutgers & NCSU Radiation Exposure Vanderbilt & Sandia Post-radiation Characterization Vanderbilt & Rutgers Theory Vanderbilt Slide 26 MURI 26 Rutgers Plans u Generation of films and devices with high-K dielectrics (HfO 2 ) and/or metal gate electrodes (Al, Ru, Pt) with 1-50nm thickness u Interface engineering: SiO x N y (vary thickness and composition) u Physical measurements of defects: STM, AFM, TEM vs particle, fluence, energy u H/D concentration and profiles, and effects on defect generation and passivation u Correlate UHV-based studies with electrical and internal photoemission measurements. u Explore different processing and growth methods. u Correlate with first principles theory. u Develop predictive understanding of radiation induced effects General goal: to examine new materials for radiation induced effects and compare with Si/SiO2/poly-Si stacks Slide 27 MURI 27 Rutgers Industrial contacts u Gusev, Guha - IBM u Liang, Tracy - Freescale u Tsai - Intel u Chambers, Columbo - TI u Vogel, Green - NIST u Gardner, Lysaght, Bersuker, Lee Sematech u Edwards, Devine AFOSR