ALD deposited ferroelectric HfO2 -...

ALD deposited ferroelectric HfO2

S. Slesazeck1, U. Schroeder1, E. Yurchuk1, J. Müller2, S. Müller1, D. Martin1, T. Schenk1,

C. Richter1,C. Adelmann3, S. Kalinin5, A. Kersch7, and T. Mikolajick1,4

3rd ALD Symposium - SEMICON Europa

October 7th 2014

1

October 7th, 2014

132 65 7

Outline

2. Stabilization of the Ferroelectric HfO2 Phase

1. Motivation: Ferroelectricity in HfO2

3. Device Application: 1T FeFET Memory

4. Summary

2S. Slesazeck et al.

SEMICON 10/2014 Grenoble

Outline



3. Device Application: 1T FeFET

4. Summary



Motivation: Ferroelectric HfO2

Ferroelectrics enablefast low power non-volatile memories

130nm FRAMp

e.g. FRAM:- current scaling limit: 130 nm

due to material properties new material necessary

TI & Ramtron

A lot of industry experienceintegrating HfO2 / ZrO2:

CMOS DRAMsub 30 nm

g g 2 2

- CMOS compatible- scalability well below 50nm- ALD process available- ferroelectric properties

chipworks



(IEDM 2011 / VLSI 2012 / IEDM 2013)

Motivation: 1T FeFET memory

Metal-GateF l t i

n+ n+

Ferroelectric

S b t tSemiconductor

Performanceadvantages:

• non-volatility p-Substrate

0“

non volatility• non-destructive

readoutl

noIdrain „0“

high Vth„1“

low Vth• low power

consumption• switching speed in

polarization

g pns-time range

• low operationvoltages

Vgate

voltages




Metal-GateF l t i + +

n+ n++ + +

Ferroelectric

S b t t

-+ -+ -+Semiconductor


• non-volatility

0“

p-Substratenon volatility• non-destructive

readoutl Idrain „0“

high Vth• low power

consumption• switching speed in g p

ns-time range• low operation

voltages

Vgate

voltages




Metal-GateF l t i

n+ n+- - -Ferroelectric

S b t t

-+ -+ -+Semiconductor


• non-volatility p-Substrate

1“

non volatility• non-destructive

readoutl Idrain „1“

low Vth• low power

consumption• switching speed in g p

ns-time range• low operation

voltages

Vgate

voltages



Outline



3. Device Application:1T FeFET

4. Summary



HfO2 phase stabilization

Amorphous HfO2 2

Anneal + DopingHigh-symmetry / high-k phases 4

Spinodal

1AnnealDe-mixing

+ DopingNon-centrosym. / Non-centrosym. /

Low-symmetry / lower-k phase

Non centrosym. / FE phase

Non centrosym. / ‚AFE‘ phase

lower k phase

Tetragonal P4 /nmc

Cubic Fm3m orTetragonal P42/nmc

depending on dopantOrthorhombic Pbc21 Tetragonal*

Monoclinic P21/c

16413

14Si

39Y

38

40Zr

13

14Si



Tetragonal/Cubic GdAlSr Al

ALD Process: doped HfO2 nanolaminates

Other precursors used for dopant supercycles:

TiN

TiPt

TiN

TiPt• tetrakis(ethylmethylamino)hafnium (TEMAHf)

• hafnium tetrachloride (HfCl4)

HfO2

TiN TiN• silicon tetrachloride (SiCl4)

• tetrakis(dimethylamino)silane (4DMAS)

TiN

SiO2• tris(dimethylamino)silane (3DMAS)

TiN

Si- wafer

Native SiO2• tris(isopropylcyclopentadienyl)gadolinium (Gd(iPrCp)3)

• tris(methylcyclopentadienyl)-yttrium (Y(MeCp)3)

• strontium di-tert-butylcyclopentadienyl (Sr(tBu3Cp)2)

• and trimethylaluminium (TMA)

O l



+ water, ozon or O2-plasma

Capacitor Route

Route

Anneal+ Pt Wet Etch

Layer depositi + Pt

dotsWet Etchdepositi

on

Silicon ElectrodeDeposition

HfO2deposition

Platinum dots

Simple capacitor processing



Effect of Si -Doping PtTiN

40

60

C/c

m2]

Electric Field [MV/cm]

Para FE AFE

TiNSi-substrate

Si:HfO2

0

20

40

lace

men

t [C

Increase of Si content

concentration

-60

-40

-20

SiO2

Elec

tric

Dis

p

0 mol % 4.4 mol % 5.6 mol % 6.6 mol % 8.5 mol %

→ Change of electrical

properties : -3 0 3 -3 0 3 -3 0 3 -3 0 3 -3 0 3E

3 5

4.0

4.5

cm2]

Effect was confirmed by

polarisation and

2.5

3.0

3.5

cita

nce

[F/

c

0 mo %

polarisation and

capacitance -voltage

measurements

1.5

2.0

-3 0 3 -3 0 3 -3 0 3 -3 0 3 -3 0 3

SiO2

Cap

ac

4,4 mol % 5,6 mol % 6,6 mol %

Electric Field [MV/cm]

8,5 mol %9 nm Si:HfO2 after 800oC AnnealPr~∫C(V)dV



Electric Field [MV/cm]E. Yurchuk et al., Thin Solid Films 2012

A. Toriumi at al. APL 86, 2006

Correlation to HfO2 phase

Ferroelectricity observed when th h bi h d i t

C. Richter BALD 2014



orthorhombic phase dominant

Different HfO2 dopants – dopant range

paraelectric

( ) ‚antiferro-electric‘ ( )

ferroelectric

0

P

paraelectric

• Ferroelectricity visible for dopands with different crystal radius

0 E

• ‚Antiferroelectricity‘ only for dopands with radius smaller than HfO2

• Dopant range larger for higher crystal radius



Schroeder et al., JSS 2012/JJAP 2014

Different HfO2 dopants - polarization

M i l i i i llMaximum polarization typically at

about 3-6 mol% dopant concentration



Schroeder et al., JJAP 2014

Outline

2. Stabilization of the Ferroelectric Phase



4. Summary



Ferroelectric Field Effect TransistorDevice Application: 1T FeFET

Memory Window28nm N-channel MFIS-FET

liner W

1

10

In+ n+

+ + +

- - -

-+

-+

-+

(mA

) LG : 28 nm

0 01

0.1

1 ITH

ain

curr

ent

erase100 ns

MW+5V

program100 ns-5V

20 nm

1 0 0 5 0 0 0 5 1 0 1 5

1E-3

0.01

n+ n++ ++

- - -+-

+-

+-

Dra• World‘s first 28nm FeFET

-1.0 -0.5 0.0 0.5 1.0 1.5 Gate bias (V)

World s first 28nm FeFET

• Memory window ~1V



E. Yurchuk et al., IEEE TED 2014

Device Application: 1T FeFETRetentionEndurance

-0.5

0.0

0.5

25 oC 85 oC 125 oCV

)Volts

)

~ 0 9V

-1.5

-1.0V TH (V

10 y

ears

0 30.60.91.2

MW

afte

r ye

ars (

V)

V t(V~ 0.9V

10-1 100 101 102 103 104 105 106 107 108

-2.0

Time (s)

1

0.00.3M 10

125 oC 85 oC 25 oC

E Yurchuk et al IEEE TED 2014

Time (s)

K Kh ll M t Th i

Memory window after 105 cycles: ~0.9VA l ti f t i h i j ti l MW

E. Yurchuk et al., IEEE TED 2014K. Khullar Master Thesis

Accumulation of asymmetric charge injection closes MW Detrap pulse can recover memory window Memory window after 10 years: ~1.0V



y y

Device Application: 1T FeFETFerroelectric FET Ferroelectric MIM CapEndurance

~ 0 9V~ 0.9V

C li i it li it d b b kd

K. Yurchuk PhD ThesisK. Khullar Master Thesis

• Cycling in capacitor limited by breakdown

• Cycling in transistor limited by charge trapping



EnduranceDevice Application: 1T FeFETFerroelectric FET Gate leakage current

0.1Number of program/erase cycles:

Endurance

1E-3

Number of program/erase cycles: 5x103 104 2x104

initial 100 103

m2 )

~ 0 9V

1E 7

1E-5 5x104 2x103

I G (A

/cm~ 0.9V

-2 -1 0 1 2

1E-7

V (V)E. Yurchuk et al., IPRS 2014

VG (V)K. Khullar Master Thesis

Gate leakage current increases with program/erase cycling



Device Application: 1T FeFETI t f i l t

10 x 1011

m2 )

Variable base level charge pumpingInterfacial traps

200

250

100 101 102 103 1040

5

m2 )

x 10

Number of cycles

NC

P

(Tra

ps/c

m

100

150

after 2x103 cycles after 103 cycles

after 5x103 cycles I C

P (mA

/cm Number of cycles

-2 -1 0 10

50after 10 cycles

initial

2 1 0 1VGB (V)

Generation of interface traps is the root cause of degradation

E. Yurchuk et al., IPRS 2014

Generation of interface traps is the root cause of degradation

Interplay between SiO2-interface and ferroelectric HfO has to

be optimized



p

DRAM like FeFET:

CH Cheng et al. IEEE EDL 35, 1, 2014

- 30nm ZrHfO in FeFET: +/- 4V switching Switching in sub-cyclesS 12

Changed operation conditions can significantly improve cycling

- Switching time: 5ns 1012 endurance, but low retention: ~10s



Comparison NOR Flash vs. AND FeFET

NOR Flash AND FeFET DRAM DRAM

F FETspec FeFET

Write/Erase Speed 1μs/2ms 10 ns/10ns ns 5ns

Read Speed 10μs 20ns ns ?

Retention 10 yrs 10 yrs >64ms 10s

Endurance 105 cycles 104 cycles >1015 >1012Endurance y 10 cycles >10 >10

Write/Erase Voltage 10-20V 5V 0.5V 4V

FeFET meets some FLASH and DRAM specifications



Scaling of FeFET – grain and domain size

Grain size~30nm

TEM

Domains and grains

Domain size~300nm

and grainsbeforedevice

structuring

Domains and grainsunderneath

250 d i

Domains and grainsunderneath

25 d iPFM 250nm device 25nm device

S l l k l bl b d b h k d

PFM

- Scaling likely possible, but needs to be checked

- low variability of switching characteristics on smallest devices



Piezo Force Microscopy

DielectricsPiezoelectrics

PyroelectricsFerroelectrics

Ref.: http://en.wikipedia.org/wiki/Piezoresponse_Force_Microscopy

- Phase: Polarization direction detectable- Local distribution

D Martin @ Oak Ridge Nat Labs



D. Martin @ Oak Ridge Nat. Labs

Piezo Force Measurements

180°3

+4.2 V0°

a.u.nm3nm

2

-4.2 V0°

1

Topography Piezo responce Phase

-180°0

- Most HfO2 grains switchable

polarization value visible two polarization direction

D. Martin et al., Ad M tMost HfO2 grains switchable

- PFM serves as base for optimization of film composition

and crystallization on simple capacitor structures

Adv. Mat.submitted

U. Schroeder et al., IWDTF 2013/ JJAP 2014



and crystallization on simple capacitor structures JJAP 2014

Outline



3. Ferroelectric Switching Behavior

5. Summary




Summary

Material:

A ferroelectric phase in HfO2 thin films can be stabilizedp 2

Ferroelectric phase most likely orthorhombic phase

Several stabilizing dopants have been identified

Ferroelectric Devices:

1T/1C: FE-HfO2 adds the 3rd dimension to FRAM scaling1T/1C: FE HfO2 adds the 3rd dimension to FRAM scaling

World‘s first 28nm FeFET device

HfO2-based FeFET added to ITRS roadmap in 2014:

Most promising ‚Emerging Memory‘ concept

FeFET meets already some DRAM and FLASH specification

Superior control of dopant concentration in ALD nanolaminates

and usbsequent crystallization of the film is mandatory



Thank you for your attention

This work was supported in part by the EFRE fund of the European Commission within the scope of technology development and in part by the Free State of Saxony

(Project: Cool Memory, Heiko, Merlin)

and by funding of the Deutsche Forschungs Gemeinschaft(DFG) (Project: Inferox)



( j )

Thanks to the FeFET – TEAM:

2 3 4

5 6 7 8 9

dand many more:

U. Schröder1, E. Yurchuk1, J. Mueller2, S. Mueller1, T. Mikolajick1

T. Boescke4, D. Martin1, D. Zhou1, J. Sundqvist2, P. Polakowski2, T. Schenk1, U. Boettger5, D. Braeuhaus5, S. Starschich5, C. Adelmann6, M.

Popovici6, T. Schloesser3, M. Trentzsch3 , M. Goldbach3, R.v. Bentum3, S. p , , , , ,Knebel1, T. Olsen1, R. Hoffmann2, J. Paul2, R. Boschke3, A. Kumar7, T.M.

Arruda7, S.V. Kalinin7, M. Alexe8, A. Morelli8, A.Kersch9, R. Maverick9


SEMICON 10/2014 Grenoble1

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ALD deposited ferroelectric HfO2 -...

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