Laboratoire L2MP 14 janvier 2005

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1 Assemblée e Générale G L2MP 14 janvier 2005 A highly reliable 3-dimensional integrated SBT ferroelectric capacitor enabling FeRAM scaling

2 L2MP (France) N. Menou (PhD), V. Madigou,, Ch. Turquat, D. Goguenheim,, V. Chevallier,, Ch. Muller IMEC (Belgium) L. Goux,, D.J. Wouters,, J. Lisoni,, M. Schwitters STMicroelectronics (Italy) C. Caputa,, R. Zambrano ESRF (France) J-L. Hodeau,, R. Barrett Collaboration Network Scientific Dissemination Invited talk: EMRS France (2004) Oral contributions: ISIF Korea (2004); Workshop Ukraine (2004) Best Poster Award: ISIF Korea (2004) 1 paper submitted in APL (Device Physics) 1 paper submitted in IEEE Transactions on Electron Devices

3 Planar (2D) Evolution in Memory Cell Structure Stack FeRAM memory cell integration 3D 3D integrated ferroelectric capacitor enabling FeRAM scaling

4 Why 3D Capacitors? 3D integrated SBT-based capacitors (SBT: 405 C) Design with larger polarization signal per unit area of the memory cell CMOS scaling trends TEM L2MP SW Pt SBT Pt IrO 2 Ir SW 0.2 µm Gain in polarization due to the electrical contribution of sidewalls (SW) Gain in P R is lower than the expected increase Electrical and microstructural behaviors of SW? L2MP's task in FLEUR (IST )

5 3D Integrated Ferroelectric Capacitors Electrical Behavior of SW

6 Poling Effect in 3D FeCAP No. cycles at 5 V 2D design 3D design P R variation from 1 st cycle % +10% % 0% % 9% SW: fatigue after 4.6 x cycles P SW R : 3.3 to 2.9 _C/cm 2 Tilt of the loop High field: change in slope

7 3D Integrated Ferroelectric Capacitors Microstructural Behavior of SW Coupled mxrf/mxrd XRD (ID18F/ESRF)

8 Integration of fluorescence spectra mxrf/mxrd XRD Methodology 20 mm 1.8 mm Chemical mapping Integration of 2D mdiffraction patterns Scan by steps of 0.2 mm "Crystallographic" mapping Out In

9 X-ray beam Patterned electrode mxrf/mxrd XRD BE: Ir edge 1.8 mm U = Ir/IrO 2 Good agreement between experimental points and fitted curve Periodicity: 2.6 µm

10 "Chemical" capacitor mxrf/mxrd XRD SBT film (3D etch) Chemical periodicity is respected Local composition variations? "Crystallographic" capacitor Crystallites orientation is not controlled Due to SW?

11 3D Integrated Ferroelectric Capacitors Microstructural Behavior of SW Synchrotron X-ray Diffraction (D2AM/ESRF)

12 2D etch 1 High Resolution XRD (115) reflection 2 3D etch Microstructural model for 3D Zone 1: SBT on BE Zone 2: SBT in SW Zone 3: SBT on SiO 2 Whole pattern fitting Drastic change in cell parameters in SW (zone 2) Composition variation?

13 3D Integrated Ferroelectric Capacitors Microstructural Behavior of SW Coupled TEM/EDS Analyses (L2MP)

14 Probe size: 90 nm EDS Analyzes Probe size: 10 nm Composition variation in sidewalls Local composition variations Bi, Sr & Ta Ø Volume of zone 2 Ø ß Effect on electrical properties ß Multilayered substrate ß Unit cell distortion

15 3D Integrated Ferroelectric Capacitors Conclusion

16 P R "Cartography" Optimization of the microstructural model Bi segregation in sidewalls Lower polarization in SW ß Decrease of overall P R

17 Bi Segregation Local composition analysis (EDS) MOCVD 405 C TEM L2MP MOCVD 440 C 0.2 µm SEM IMEC Bi segregation in SW 440 C Leakage current density ß Short circuits ß Lower P R