Accurate modeling of Quantum-Dot based Multi Tunnel Junction Memory : Optimization and process dispersion analyses for DRAM applications

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Alyson Johnson
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1 Accuate modelig of Quatum-Dot baed Multi Tuel Juctio Memoy : Optimizatio ad poce dipeio aalye fo DRAM applicatio C. Le Roye, G. Le Caval, D. Faboulet (CEA - LETI M. Saque (CEA - DRFMC

2 Outlie Itoductio Memoy cell deciptio Piciple of the memoy Techological paamete The imulatio model Electical modelig of the memoy cell Phyic of Double Tuel Juctio Reult Ideal dot Impact of techological dipeio Cocluio 2

3 Itoductio Limitig facto of covetioal memoie : calig : moe ad moe difficult DRAM itegatio : limited by the ize of the toage capacito Alteative cocept of memoie : Magetic RAM NOVORAM Quatum dot memoie : Naocytal baed memoy Multi-Tuel-Juctio Memoy : «MTJM» 3

4 Memoy cell deciptio Piciple of the MTJ Memoy Achitectue imila to Flah Memoy Wite / Eae : «igle-electo» tuel cuet betwee the Cotol Gate (CG ad Cotol Gate t ox Floatig Gate SiO 2 Dot ( ~.5 m the Floatig Gate (FG Souce Dai Data etetio eued by : MOSFET : L = 50 m thick High K gate iulato the Coulomb blockade pheomeo due to the ao-dot 4

5 Techological paamete Memoy cell deciptio Key-poit : popetie of the dot Uual appoach : Spheical dot Without dipeio CG Poly Si.5m.5m.5m SiO 2 Thi tudy : Ellipoidal dot with ize dipeio FG S D MOSFET Ditace betwee gate : cotat i thi tudy 5

6 Outlie Itoductio Memoy cell deciptio Piciple of the memoy Techological paamete The imulatio model Electical modelig of the memoy cell Phyic of Double Tuel Juctio Reult Ideal dot Impact of techological dipeio Cocluio 6

7 The Simulatio model Electical modelig of the Memoy cell Electo tuelig decibed by Tuel Juctio CG FG Tuel Reitace R t Juctio Capacitace C J R t C J S D Deity of dot = cm -2 o igificat itedot ifluece * oly vetical cuet path * cetal elemet : the Double Tuel Juctio CG V... U C gg Souce I I 2 I Q FG Dai Double Tuel Juctio * Le Roye et al, Modelig ad Simulatio of Sigle-Electo Multi Tuel Juctio Memoy, MSM, Apil

8 d Q d t FG = k = V CG = V + The Simulatio model Electical modelig of the Memoy cell Equatio decibig the Memoy cell I k U U = α V + CG (V Q C FG FG, Double Tuel juctio I(V CG V... U C gg Souce I I 2 I Q FG Dai Double Tuel Juctio Need fo : I k (V Model Voltage -Vc +Vc 8

9 The Simulatio model Phyic of the Double Tuel Juctio p t Mate-Equatio model :. elate the pobabilitie of the chage tate of the dot to the tuelig ate =,+ p + +, p - ( +, + -, p (V,q (V,q q 2 V 2 (V,q (V,q I(V p : pobability (q = e +, : taitio ate betwee the tate ad «+», +, = (V,e + 2(V,e I(V chaacteitic icludig taiet effect : [ V(t ] = e p (t [ (V, - (V, ] + I 9

10 The Simulatio model Phyic of the Double Tuel Juctio Fo the MTJM cell, 3 elevat chage tate : q = -e, 0, +e 3 diffeetial equatio p& p& p& - 0 = = = -,0 0,,0 p p p ,- 0, 0,- p p p (,0 + Fo the MTJM cell, I(V model of the Double Tuel Juctio : [ V(t ] = e p (t [ (V,0 - (V,0 ]- e p (t (V,-e + e p (t (V, e I 0 - -,0 p 0 (V,q (V,q q V 2 2 (V,q (V,q I(V 0

11 The Simulatio model Phyic of the Double Tuel Juctio (V,0 the tuelig ate («othodox theoy» q = 0 V (V, q e 2 C = C = + J 0 = 2 E e 2 e R cof t V - VC (V e - exp - 2 k E cof ( hπ² = 8 m0 Need fo accuate modelig of ( V - V 2 R B ² T + C R ² (V,0 Cofiemet eegy i the dot, E cof Capacitace C J, Cgg : 3D imulato (ICARE* + DoE Tuel eitace R t (V H V R V R H V 2 (V,0 2 (V,0 * S. Putot et al, A Fat ad Accuate Computatio of Itecoect Capacitace, IEDM 99 R H

12 The Simulatio model Phyic of the Double Tuel Juctio Tuel eitace h / e² Rt,(V = T(V t,(v R t,(v R V V 2 Dot chage: q = 0 R t,2(v2 (V R t,2 2 e.v T : tuel tapaecy WKB model Regite coectio (eceay becaue vey thi baie Impact of R t (V modelig o device behavio : Wite Retetio ou model cotat Rt time ( 2

13 Outlie Itoductio Memoy cell deciptio Piciple of the memoy Techological paamete The imulatio model Electical modelig of the memoy cell Phyic of Double Tuel Juctio Reult Ideal dot Impact of techological dipeio Cocluio 3

14 Reult Geometie Witig pule (t Wite, V Wite Ou model Q FG (t Vt (t Retetio Vt = 0.5 V t Wite 0. 0 Retetio time time ( 4

15 Reult Ellipoidal dot without ize dipeio L = W = 50 m Deity =.6 0 cm -2 T = 300 K d CG-FG = 4.5 m t Wite = 0 V Wite = 5 V R V Cotat d CG-FG Rv = m Rv =.25 m Rv =.5 m DRAM limit R H R H,5 2 2,5 3 Hoizotal adiu R (m H Retetio time: highly eitive to geomety DRAM applicatio Retetio time > 2 R H, R v <m! 5

16 Reult Impact of techological dipeio R H : gauia ditibutio < R H > = m σ Rh = 0-5 % R V : m Retetio time epatitio : log-omal ditibutio Allow yield etimatio (citeio : Retetio time > igma: 0 % Log-Nomal igma: 5% Log-omal Yield : 98 % Yield : 83 % Retetio time ( Retetio time ( 6

17 Reult Impact of techological dipeio R H & R V : gauia ditibutio < R H > = < R V > = m σ Rh = 0 %, σ Rv = 3 % Yield : 98 % 87 % data Log Nomal Retetio time ( 7

18 Cocluio Modelig of the MTJM cell, takig ito accout : Coulomb blockade pheomeo Quatum cofiemet i the dot Taiet effect Techological dipeio Applicatio : coditio fo DRAM feaibility (fo the 50m ode Impact of dot ize ad dot ize dipeio Reult : pecificatio fo dot : adiu < m! dot ize cotol : eceity of extemely low dipeio. 8

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