Novel high-k materials Can we nominate candidates for the 22 and the 16 nm nodes?

1. Novel high-k materialsCan we nominate candidates for the 22 and the 16 nm nodes? Olof Engstrom Chalmers University of Technology Paul Hurley Tyndall National Institute Octavian Buiu University of Liverpool Max Lemme AMO

2. Outline • Why high-k? • Essential properties needed • Why are rare-earth oxides interesting? • Comparison between different candidates • Finalists?

3. Bulk MOS: Oxide voltage vs gate voltage Oxide thickness= 10 [Å] k 3.9 7 15 25 Silicon doping: 4 1018cm-3 O M S qYs EF V Oxide voltage [V] Gate voltage [v]

4. F The k-value should be ”lagom” For Lg = 70 nm SiO2 k = 10 k = 25 k = 50 Mohapatra et al, IEEE Trans. Electron. Dev. 49, 826 (2002)

5. Essential properties • k-values • Energy offsets DEc and DEv • Reactivity with silicon • Hygroscopicity • Structural stability • Interface states • Charge carrier traps DEc DEv

6. Metals of interest

7. Polarizability and k-value Clausius-Mosotti D. G. Schlom et al, Thin films and heterostructures for oxide electronics, (Springer, 2005), p. 31

8. Energy offset vs. k-value Borders for the 22 nm LSTP bulk node: 10-2 A/cm2 EOT=0.6 nm Vox= 1V (Target) Requires k DE ≈ 70 eV LaLuO3 O. Engström, B. Raeissi, S. Hall, O. Buiu, M.C. Lemme, H.D.B. Gottlob, P.K. Hurley, K. Cherkaoui, SSE, 51, 622 (2007)

9. Reactivity La2O3 (evap) Kim et al SSE 49, 825 (2005) Gd2O3 (MBE) Czernohorsky et al APL 88, 152905 (2006) 950 C As grown 550 C Lu2O3 (ALD) Scham et al Topics in Appl. Phys. Vol. 106, p. 153 (Springer, 2007)

10. DG1000C SiO2 Reactivity For Si + O DG1000C < 0 M + SiO2 DG1000C MSi + SiO2 Si + MO M + MSiO D. G. Schlom et al, Thin films and heterostructures for oxide electronics, (Springer, 2005), p. 31

11. water + oxide hydroxide Hygroscopicity K.Kakushima, K.Tsutsui, S-I. Ohmi, P.Ahmet V.R. Rao and H. Iwai in Rare earth oxide thin films ( Springer, 2007), p. 345

12. Structural stability Example: LaLuO3 APL, 89, 222902 (2006)

13. 1 0,1 0,01 1E-3 1E-4 1E-5 1E-6 1E-7 1E-8 1E-9 0,4 0,6 0,8 1,0 1,2 1,4 1,6 Leakage Gd2O3 [2], HfO2[1], ZrO2[1] [A/cm2] HfGdO [3] 3 HfO2 [5] (with HfSiO IL) HfO Leakage current 2 Lu2O3 [4] with epitaxial Lu2O3 - silicate IL) and La2O3 [1] ZrO 2 EOT [nm] [1] H. Iwai et al, Proc. IEDM, 2002 [2] H.D.B. Gottlob et al, IEEE Electron Dev. Lett. 27, 814 (2006) [3] S. Govindarajan et al, APL 91, 062906 (2007) [4] P. Darmawan et al, APL 91, 092903 (2007) [5] A. Ogawa et al Microel. Eng. 84, 1861 (2007)

14. Experimental C = f (V,freq.) HfO2 React. sputt. Gd2O3 ALD Gd2O3 MBE B.Raeissi, J.Piscator, O.Engström, S.Hall, O.Buiu, M.C.Lemme, H.D.B.Gottlob, P.Hurley, K.Cerkaoui and H.J.Osten, Proc. ESSDERC, 2007, p 287

15. LaSiOx LaSiOx E-beam evap. LaSiOx/Si interface P.K.Hurley, K.Cherkaoui, E.O’Connor, M.C.Lemme, H. D.B. Gottlob, M.Schmidt , S.Hall, Y.Lu, O.Buiu, B.Raeissi, J. Piscator and O.Engstrom, J. Electrochem. Soc., in press

16. Dit for HfO2, Gd2O3 and LaSiOx P.K.Hurleya, K.Cherkaoui, E.O’Connor, M.C.Lemme, H. D.B. Gottlob, M.Schmidt , S.Hall, Y.Lu, O.Buiu, B.Raeissi, J. Piscator and O.Engstrom, J. Electrochem. Soc., in press

17. Nominees Too low k DEc,v Wild cards Exists only in Andromeda Final solution: The Nominees

18. Finalists

19. Conclusion Lantanum based oxides seem worth a bid but fortunately for academic people there is a lot more work to do!

20. Theoretical C=f(V,freq.) C [F] C-V Gate voltage [V] Dit = f(DGn) Dit [m-2eV-1] DGn[eV] log sn = f(DGn) sn [m2] DGn[eV]

21. F = V/d P/(3e0) Floc= F + P/(3e0) The concept of polarization P = (1/Vm) ac Floc a = 4 p e0 ac [A3]

22. - + High-k oxide Fischetti et al, PRB 90, 4587 (2001) LO-phonon Si Large a means sloppier material Remote phonon scattering w = (spring constant/mass)1/2