Novel high-k materials

Can we nominate candidates for the 22 and the 16 nm nodes?

Olof EngstromChalmers University of Technology

Paul HurleyTyndall National Institute

Octavian BuiuUniversity of Liverpool

Max LemmeAMO

Outline

• Why high-k?

• Essential properties needed

• Why are rare-earth oxides interesting?

• Comparison between different candidates

• Finalists?

Bulk MOS: Oxide voltage vs gate voltage

0 0.5 1 1.5

-0.2

0

0.2

0.4

0.6

Oxide thickness= 10 [Å]k3.9 7 15 25

Silicon doping: 4 1018 cm-3

Oxi

de v

olta

ge [

V]

Gate voltage [v]

M S

qsEF

V

O

The k-value should be ”lagom”

Mohapatra et al, IEEE Trans. Electron. Dev. 49, 826 (2002)

F

For Lg = 70 nmSiO2

k = 10k = 25

k = 50

Essential properties

Ec

Ev

•k-values•Energy offsets Ec and Ev

•Reactivity with silicon•Hygroscopicity•Structural stability•Interface states•Charge carrier traps

Group**

1 IA 1A

18

VIIIA 8A

1 1 H

1.008

2

IIA 2A

13

IIIA 3A

14

IVA 4A

15

VA 5A

16

VIA 6A

17

VIIA 7A

2 He 4.003

2 3

Li 6.941

4 Be 9.012

5 B

10.81

6 C

12.01

7 N

14.01

8 O

16.00

9 F

19.00

10 Ne 20.18

8 9 10

3 11

Na 22.99

12 Mg 24.31

3

IIIB 3B

4

IVB 4B

5

VB 5B

6

VIB 6B

7

VIIB 7B

------- VIII -------

------- 8 -------

11

IB 1B

12

IIB 2B

13 Al

26.98

14 Si

28.09

15 P

30.97

16 S

32.07

17 Cl 35.45

18 Ar 39.95

4 19 K

39.10

20

Ca 40.08

21 Sc 44.96

22 Ti

47.88

23 V

50.94

24 Cr 52.00

25 Mn 54.94

26 Fe 55.85

27 Co 58.93

28 Ni 58.69

29 Cu 63.55

30 Zn 65.39

31 Ga 69.72

32 Ge 72.59

33 As 74.92

34 Se 78.96

35 Br 79.90

36 Kr 83.80

5 37

Rb 85.47

38 Sr 87.62

39 Y

88.91

40 Zr 91.22

41 Nb 92.91

42 Mo 95.94

43 Tc (98)

44 Ru 101.1

45 Rh 102.9

46 Pd 106.4

47 Ag 107.9

48 Cd 112.4

49 In

114.8

50 Sn 118.7

51 Sb 121.8

52 Te 127.6

53 I

126.9

54 Xe 131.3

6 55

Cs 132.9

56 Ba 137.3

57 La

*138.9

72 Hf 178.5

73 Ta 180.9

74 W

183.9

75 Re 186.2

76 Os 190.2

77 Ir

190.2

78 Pt 195.1

79 Au 197.0

80 Hg 200.5

81 Tl

204.4

82 Pb 207.2

83 Bi 209.0

84 Po (210)

85 At (210)

86 Rn (222)

7 87 Fr (223)

88 Ra (226)

89 Ac ~(227)

104 Rf (257)

105 Db (260)

106 Sg (263)

107 Bh (262)

108 Hs (265)

109 Mt (266)

110 Ds (271)

111 Uuu (272)

112 Uub (277)

114

Uuq (296)

116

Uuh (298)

118

Uuo (?)

Lanthanide Series*

58 Ce 140.1

59 Pr 140.9

60 Nd 144.2

61 Pm (147)

62 Sm 150.4

63 Eu 152.0

64 Gd 157.3

65 Tb 158.9

66 Dy 162.5

67 Ho 164.9

68 Er 167.3

69 Tm 168.9

70 Yb 173.0

71 Lu 175.0

Actinide Series~

90 Th 232.0

91 Pa (231)

92 U

(238)

93 Np (237)

94 Pu (242)

95 Am (243)

96 Cm (247)

97 Bk (247)

98 Cf (249)

99 Es (254)

100 Fm (253)

101 Md (256)

102 No (254)

103 Lr (257)

** Groups are noted by 3 notation conventions.

Metals of interest

Polarizability and k-value

]43

11[

]43

21[

mV

mV

k

Clausius-Mosotti

D. G. Schlom et al, Thin films and heterostructures for oxide electronics, (Springer, 2005), p. 31

Si(4+) Al(3+) Hf(4+) Zr(4+) Y(3+) La(3+)Ce(3+)Pr(3+)Gd(3+)Yb(3+)Lu(3+)0

1

2

3

4

5

6

Pol

ariz

abili

ty,

Ion

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 E ≈ 70 eV

O. Engström, B. Raeissi, S. Hall, O. Buiu, M.C. Lemme, H.D.B. Gottlob, P.K. Hurley, K. Cherkaoui, SSE, 51, 622 (2007)

LaLuO3

Reactivity

Lu2O3 (ALD)Scham et alTopics in Appl. Phys. Vol. 106, p. 153(Springer, 2007)

La2O3 (evap)Kim et alSSE 49, 825 (2005)

Gd2O3 (MBE)Czernohorsky et alAPL 88, 152905 (2006)

550 C 950 CAs grown

Reactivity

Si + MO

M + SiO2

MSi + SiO2

M + MSiO

G1000C

For Si + O G1000C < 0

G1000C

SiO2

Al2O3 ZrO2 HfO2 Yb2O3 Lu2O3 Gd2O3 Dy2O3Sm2O3 Pr2O3 La2O30

100

200

300

400

500

G [k

J/m

ol]

OxideD. G. Schlom et al, Thin films and heterostructures for oxide electronics, (Springer, 2005), p. 31

Hygroscopicity

SiO2 ZrO2 Yb2O3 Lu2O3 Gd2O3 Dy2O3 Sm2O3 Pr2O3 La2O30,0

0,5

1,0

1,5

2,0

2,5

EO

T (

120

hrs)

/EO

T (

fres

h)Oxide

Eu2O3 ZrO2 Yb2O3 Lu2O3 Gd2O3 Dy2O3 Sm2O3 Pr2O3 La2O31E-3

0,01

0,1

1

10

100

1000

J 12

0 h

rs/J

fre

sh

Oxide

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

water + oxide hydroxide

Structural stability

APL, 89, 222902 (2006)

Example: LaLuO3

0,4 0,6 0,8 1,0 1,2 1,4 1,61E-9

1E-8

1E-7

1E-6

1E-5

1E-4

1E-3

0,01

0,1

1

Leakage

Gd2O3 [2], HfO2[1], ZrO2[1]

HfGdO [3]

Lu2O3 [4]with epitaxialLu2O3 - silicate IL)

[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)

Le

aka

ge

cu

rre

nt

[A/c

m2]

EOT [nm]

HfO2

andZrO2

3

La2O3 [1]

HfO2 [5](with HfSiO IL)

Experimental C = f (V,freq.)

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

HfO2

React.sputt.

LaSiOx/Si interface

-2 -1 0 10.000

0.005

0.010

0.015

0.020

0.025

0.030

1 kHz 10 kHz 100 kHz 1 MHz

Wafer X3361-19 Site 19a18

Ca

pa

cit

an

ce

(F/m

2 )

Voltage Vg (V)

LaSiOx

E-beamevap.

LaSiOx

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

Dit for HfO2, Gd2O3 and LaSiOx

0,4 0,6 0,8 1,0

2

4

6

8

10

10000 100000 10000000.0015

0.0020

0.0025

0.0030

0.0035

Gp/

Gp/

Vg=-0.75V

Dit=5x1012 eV-1cm-2

HfO2 ALD 1.4nm E

OT (Sample 1)

HfO2 sputtered 18nm E

OT (Sample 4)

Gd2O

3 MOCVD 17nm E

OT (Sample 5)

Gd2O

3 ALD 13.5nm E

OT (Sample 6)

LaSiOx e-beam 4nm E

OT (Sample 9)

Dit (x

1012

cm

-2 e

V-1)

E-Ev (eV)

0.83 0.92

0.09 eVLaSiOx 4 nm E

OT

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

Group**

1 IA 1A

18

VIIIA 8A

1 1 H

1.008

2

IIA 2A

13

IIIA 3A

14

IVA 4A

15

VA 5A

16

VIA 6A

17

VIIA 7A

2 He 4.003

2 3

Li 6.941

4 Be 9.012

5 B

10.81

6 C

12.01

7 N

14.01

8 O

16.00

9 F

19.00

10 Ne 20.18

8 9 10

3 11

Na 22.99

12 Mg 24.31

3

IIIB 3B

4

IVB 4B

5

VB 5B

6

VIB 6B

7

VIIB 7B

------- VIII -------

------- 8 -------

11

IB 1B

12

IIB 2B

13 Al

26.98

14 Si

28.09

15 P

30.97

16 S

32.07

17 Cl 35.45

18 Ar 39.95

4 19 K

39.10

20

Ca 40.08

21 Sc 44.96

22 Ti

47.88

23 V

50.94

24 Cr 52.00

25 Mn 54.94

26 Fe 55.85

27 Co 58.93

28 Ni 58.69

29 Cu 63.55

30 Zn 65.39

31 Ga 69.72

32 Ge 72.59

33 As 74.92

34 Se 78.96

35 Br 79.90

36 Kr 83.80

5 37

Rb 85.47

38 Sr 87.62

39 Y

88.91

40 Zr 91.22

41 Nb 92.91

42 Mo 95.94

43 Tc (98)

44 Ru 101.1

45 Rh 102.9

46 Pd 106.4

47 Ag 107.9

48 Cd 112.4

49 In

114.8

50 Sn 118.7

51 Sb 121.8

52 Te 127.6

53 I

126.9

54 Xe 131.3

6 55

Cs 132.9

56 Ba 137.3

57 La

*138.9

72 Hf 178.5

73 Ta 180.9

74 W

183.9

75 Re 186.2

76 Os 190.2

77 Ir

190.2

78 Pt 195.1

79 Au 197.0

80 Hg 200.5

81 Tl

204.4

82 Pb 207.2

83 Bi 209.0

84 Po (210)

85 At (210)

86 Rn (222)

7 87 Fr (223)

88 Ra (226)

89 Ac ~(227)

104 Rf (257)

105 Db (260)

106 Sg (263)

107 Bh (262)

108 Hs (265)

109 Mt (266)

110 Ds (271)

111 Uuu (272)

112 Uub (277)

114

Uuq (296)

116

Uuh (298)

118

Uuo (?)

Lanthanide Series*

58 Ce 140.1

59 Pr 140.9

60 Nd 144.2

61 Pm (147)

62 Sm 150.4

63 Eu 152.0

64 Gd 157.3

65 Tb 158.9

66 Dy 162.5

67 Ho 164.9

68 Er 167.3

69 Tm 168.9

70 Yb 173.0

71 Lu 175.0

Actinide Series~

90 Th 232.0

91 Pa (231)

92 U

(238)

93 Np (237)

94 Pu (242)

95 Am (243)

96 Cm (247)

97 Bk (247)

98 Cf (249)

99 Es (254)

100 Fm (253)

101 Md (256)

102 No (254)

103 Lr (257)

** Groups are noted by 3 notation conventions.

Final solution: The Nominees

Nominees

Too low k Ec,v

Wild cards

Exists only in Andromeda

Finalists

Pr2O3 La2O3 Gd2O3 LaLuO3 HfO2 ZrO2

k x DEc 66 69 42 67 35 38

k x DEv Low 66 31 67 83 80

Reactivity High High Low High High High

Hygroscop. Low High High Low Low Low

Struct. stab. Low Low High High Low Low

Conclusion

there is a lot more work to do!

Lantanum based oxides seem worth a bid

but fortunately for academic people

Theoretical C=f(V,freq.)

C-V

Dit = f(Gn)

log n = f(Gn)

-0.25 0 0.25 0.5 0.75 1 1.250

5 10-10

1 10-9

1.5 10-9

2 10-9

2.5 10-9

0 0.1 0.2 0.3 0.4 0.5

3 1017

4 1017

5 1017

6 1017

7 1017

0 0.1 0.2 0.3 0.4

-24

-23

-22

-21

0 0.1 0.2 0.3 0.4 0.50

5 1016

1 1017

1.5 1017

2 1017

2.5 1017

3 1017

0.2 0.25 0.3 0.35 0.4

-22

-21.5

-21

-20.5

-20

0 0.2 0.4 0.6 0.8 10

5 10-10

1 10-9

1.5 10-9

2 10-9

C [

F]

Gate voltage [V]

Gn[eV]

Gn[eV]

Dit

[m-2eV

-1]

n [

m2 ]

The concept of polarization

F = V/d

P/(3

Floc= F + P/(3

P = (1/Vm) c Floc c [A3]

Large means sloppier material

+-

spring constant/mass)1/2

Si

High-koxide

LO-phonon

Remote phonon scattering

Fischetti et al, PRB 90, 4587 (2001)

SiO2

Al2O3

ZrO2

HfO2

ZrSiO4

0,00 0,05 0,10 0,15 0,20 0,25 0,30

Fröhlich coupling constant

Oxi

de