Characterization of Nanoscale Dielectrics or What characterizes dielectrics

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 Gmb. H 3 Tyndal Laboratories 4 Liverpool University

Questions at issue • How long can Hf. O 2 be used? • How to find the road to higher-k, higher offset dielectrics? • Problems in connection with bulk and SOI

Hf. O 2

High-k Metal Gate Ni Hf. O 2 Si Tyndall : e-beam evaporation Liverpool: Mo. CVD, ALD Chalmers: Reactive sputtering, ALD AMO: MBE & metallization AMO, Liverpool, Chalmers and Tyndall

High-k Metal Gate (100)Si/Si. Ox(0. 6 nm)/Hf. O 2(3. 5 nm)/Ni JV Dispersion: 65 sites 55 umx 55 um Tox (max/min) = 42. 9Å/41. 4Å =0. 15Å SINANO Exchange: Tyndall Chalmers Nov 2006 : Study of Bulk Defects in Hf. O 2

(100)Si/Si. Ox/Hf. O 2/Ti. N System Interface defects: Origin and Annealing Hf. O 2 by ALD • • p Si n Si P. K. Hurley, K. Cherkaoui, and A. W. Groenland “Electrically active interface defects in the (100)Si/Si. Ox/Hf. O 2/Ti. N system: Origin, Instabilities and Passivation”, Invited paper: ECS, Cancun, Mexico, October 2006 SINANO Acknowledged

Hf. O 2/Ti. N n channel MOSFETs Mobility degradation: Interface States Hf. O 2 by ALD ICP(1 MHz) -ICP (1 k. Hz) Dit = 4. 0 x 1010 cm-2 Interface states do not limit mobility (DIT <5. 0 x 1010 cm-2)

Hf. O 2/Ti. N n channel MOSFETs Mobility degradation mo [cm 2/Vs] 100000 10000 msr mc mph 1000 mo (fitting) mo (measured) 100 0 100 200 300 Temperature [K] Remote phonon scattering term limits mobility above temperature 50 K. Presented at EMRS Symposium L, 2006: SINANO acknowledged Weber et al, Proc. ESSDERC, 2005, p. 379 400

Oxide defects, ALD Hf. O 2 Johansson et al, subm. JAP Gavartin et al, JAP 97, 053704 (2005)

Absorption constant [arb. units] Hafnium silicate Spectroscopic ellipsometry Mitrovic et al, manuscript submitted

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(<Z>) 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(<Z>) 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(<Z>) 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

Epitaxial Gd 2 O 3 with Ni. Si gate electrodes • • 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

SOI FD MOSFET Single gate x Double gate Lg From Risch, SSE 50, 527 (2006) ”natural length”

Conduction band shape for an SOI FD DG MSFET g (a) 10 5 3 Ec [e. V] g=5 (b) Source Drain x [nm]

Silicon thickness for FD DG SOI MOSFETs in the 22 nm LSTP node La 2 O 3 t. Si [nm] Gd 2 O 3 Hf. O 2 Si. O 2 Lg/l

Phonon and interface scattering in thin silicon layers Phonon modes Mobility Sotomayor-Torres et al, Phys. Stat. Sol. 1, 2609 (2004) Uchida & Takagi, APL 82, 2916 (2003) Theory Donetti et al, JAP, 100, 013701 (2006)

Summary High-k for the 22 nm LSTP node • Bulk: – So far only La 2 O 3, La. Al. O 3 seem to pass • SOI: – Si. O 2 cannot be used neither for DG nor GAA – Probably Hf. O 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!