Characterization of Nanoscale Dielectrics or What characterizes dielectrics needed for the 22 nm node? O. Engstrom 1, M. Lemme 2, P.Hurley 3 and S.Hall 4 1 Chalmers University of Technology 2 AMO GmbH 3 Tyndal Laboratories 4 Liverpool University
Questions at issue How long can HfO 2 be used? How to find the road to higher-k, higher offset dielectrics? Problems in connection with bulk and SOI
HfO 2
High-k Metal Gate AMO, Liverpool, Chalmers and Tyndall Ni Si HfO 2 Tyndall : e-beam evaporation Liverpool: MoCVD, ALD Chalmers: Reactive sputtering, ALD AMO: MBE & metallization
High-k Metal Gate SINANO Exchange: Tyndall Chalmers Nov 2006 : Study of Bulk Defects in HfO 2 T ox (max/min) = 42.9Å/41.4Å =0.15Å JV Dispersion: 65 sites 55umx55um (100)Si/SiO x (0.6nm)/HfO 2 (3.5nm)/Ni
(100)Si/SiO x /HfO 2 /TiN System Interface defects: Origin and Annealing p Sin Si P.K.Hurley, K. Cherkaoui, and A.W. Groenland “Electrically active interface defects in the (100)Si/SiOx/HfO2/TiN system: Origin, Instabilities and Passivation”, Invited paper: ECS, Cancun, Mexico, October 2006 SINANO Acknowledged HfO 2 by ALD
HfO 2 /TiN n channel MOSFETs Mobility degradation: Interface States D it = 4.0 x cm -2 I CP (1 MHz) -I CP (1 kHz) Interface states do not limit mobility (D IT <5.0 x cm -2 ) HfO 2 by ALD
HfO 2 /TiN n channel MOSFETs Mobility degradation Presented at EMRS Symposium L, 2006: SINANO acknowledged Temperature [K] o [cm 2 /Vs] sr cc ph o (fitting) o (measured) Remote phonon scattering term limits mobility above temperature 50 K. Weber et al, Proc. ESSDERC, 2005, p. 379
Gavartin et al, JAP 97, (2005) Johansson et al, subm. JAP Oxide defects, ALD HfO 2
Mitrovic et al, manuscript submitted Hafnium silicate Spectroscopic ellipsometry Absorption constant [arb. units]
The road to higher k and higher band offset values
Scaling problem of the bulk MOSFET: Shorter channel length requires increased doping under the channel which requires higher capacitive coupling between gate and channel which in turn requires thinner gate insulator material
k=f( ) Clausius-Mosotti O. Engström, B. Raeissi, S. Hall, O. Buiu, M.C. Lemme, H.D.B. Gottlob, P.K. Hurley, K. Cherkaoui, Proc. ULIS, 2006, subm. To SSE
k=f( ) O. Engström, B. Raeissi, S. Hall, O. Buiu, M.C. Lemme, H.D.B. Gottlob, P.K. Hurley, K. Cherkaoui, Proc. ULIS, 2006, subm. To SSE
k=f( ) O. Engström, B. Raeissi, S. Hall, O. Buiu, M.C. Lemme, H.D.B. Gottlob, P.K. Hurley, K. Cherkaoui, Proc. ULIS, 2006, subm. To SSE
Offset value = f(heat of formation) O. Engström, B. Raeissi, S. Hall, O. Buiu, M.C. Lemme, H.D.B. Gottlob, P.K. Hurley, K. Cherkaoui, Proc. ULIS, 2006, subm. To SSE
The 22 nm node border Borders for the 22 nm LSTP node O. Engström, B. Raeissi, S. Hall, O. Buiu, M.C. Lemme, H.D.B. Gottlob, P.K. Hurley, K. Cherkaoui, Proc. ULIS, 2006, subm. To SSE
Gate insulators for SOI
H.D.B. Gottlob et al., IEEE EDL, Vol. 27, No. 10, October, 2006 ITRS targets for 2012 EOT given here for a quantum mechanical correction of CET by 0.3 nm Epitaxial Gd 2 O 3 with NiSi gate electrodes
Single gate Double gate From Risch, SSE 50, 527 (2006) SOI FD MOSFET LgLg x ”natural length”
E c [eV] x [nm] (a) Source Drain x [nm] (b) Source Drain Conduction band shape for an SOI FD DG MSFET
t Si [nm] L g / SiO 2 Gd 2 O 3 HfO 2 La 2 O 3 Silicon thickness for FD DG SOI MOSFETs in the 22 nm LSTP node
Sotomayor-Torres et al, Phys. Stat. Sol. 1, 2609 (2004) Donetti et al, JAP, 100, (2006) Uchida & Takagi, APL 82, 2916 (2003) Phonon and interface scattering in thin silicon layers Phonon modes Theory Mobility
Summary High-k for the 22 nm LSTP node Bulk: –So far only La 2 O 3, LaAlO 3 seem to pass SOI: –SiO 2 cannot be used neither for DG nor GAA –Probably HfO 2 can be used for GAA –For DG La 2 O 3 seems to be necessary, but Gd 2 O 3 may be an alternative Brask-lapp: Things may change!