マテリアル先端リサーチインフラ オンラインセミナー『原子層堆積技術（ALD）による成膜技術』

Super high-dielectric constant AlOx/TiOy nanolaminates
deposited by the atomic layer deposition technique(for diamond MOSFETs)
劉 江偉（Jiangwei Liu）
独立研究者
機能性材料研究拠点
国立研究開発法人 物質・材料研究機構
Co-authors:
小出 康夫、達 博＠NIMS
Elida de Obaldia， Orlando Auciello@University of Texas at Dallas, USA

BackgroundWhy diamond?
Property (Relative to Si)

SiGaAsSiC

GaN

Diamond

Band gap energy
Critical breakdown field
Thermal conductivity
Thermal expansion coefficient
Dielectric constantElectron mobility
Hole mobility
Saturated carrier velocity
On-losses decrease (BFOM)

1
11
1
1
1
1
11

1.3
1.3
0.3
1.6
1.1
5.7
0.7
1.2
13.8

3
12.3
3.1
1.6
0.9
0.7
0.1
2
17.0

3.1
11.7
0.9
2.2
0.8
0.8
0.4
2.2
19.0

5
33.3
13.3
0.03
0.5
3.0
6.3
2.7
187.5

Switching loss decrease (BHFFOM)

1

9.6

105.9

109.5

6986

Power-frequency product (JFOM)

1

2.4

605

662

8083

Thermal limitation (KFOM)

1

0.16

4.6

1.5

30.9

EC vs 2JFOM  ()2

EC: Breakdown field
vs : Saturation velocitycvs 1/2
KFOM   T ()4

σT: Thermal conductivity
c: Light speed
ε: Dielectric constant

B. J. Baliga, IEEE Electron
Dev, Lett. 10, 455 (1989).

Background

Why AlOx/TiOy gate nanolaminate?
k:~1000
Super-high dielectric constant AlOx/TiOy nanolaminate

Maxwell-Wagner effect  Charge accumulation at the interface.
Buffer layer is necessary for low leakage current density.

Li, Auciello et al., JAP 110, 024106 (2011).
AlOx/TiOy nanolaminate deposition

Ultratech savannah, USA

BackgroundAtomic layer deposition equipment for high-k materials
2009~now

2012~2021

2021~now

2018

Picosun Altech, Japan@NIMS

Ensure Nanotech. China@Tokyo University & NIMS

Samco, Japan@NIMS

Ultratech savannah, USA@University of Texas, Dallas

Chemical deposition  Physical pulse/purge process Two precursors
TMA+H2O

TMA+O32 Al (CH 3 )3  O3  Al2O3  3C2 H 6

Merits:✓ Low temperature process✓ Controllable film thickness✓ Corresponding to complex
device structures

Experimental and Results

Metal/AlOx/TiOy nanolaminate/metal
AlOx/TiOx
Thickness

Precursor

MultilayerThickness

Buff. Lay.
(AlOx)

Total Th.

Tem.

0.507/0.535 nm

water

156.3 nm

5.35 nm161.7 nm

250 ºC 1.78 × 10-6 A cm-2 0.76 μF cm-2

1380.321/0.702 nm

water

153.45 nm

5.35 nm158.8 nm

250 ºC 1.53 × 10-6 A cm-2 1.24 μF cm-2

2230.321/0.702 nm

ozone

153.45 nm

5.35 nm158.8 nm

250 ºC 1.38 × 10-3 A cm-2 0.14 μF cm-2

23.60.321/0.702 nm

water

52.88 nm

5.35 nm58.23 nm

250 ºC 2.23 × 10-7 A cm-2 1.69 μF cm-2

1110.321/0.72 nm

water

52.05 nm

5.35 nm

57.4 nm

150 ºC 2.11 × 10-7 A cm-2 0.83 μF cm-2

53.8

AlOx/TiOy
nanolaminate
thickness
0.507/0.535 nm

AlOx/TiOy
nanolaminate
thickness
0.321/0.702 nm

Leakage current
at -2.5 VCmaxk

Depositionprecursor
ozone

Total
thickness
effect58.23 nmDeposition
temperatureeffect250 ºC

Deposition
temperatureeffect250 ºC

Depositionprecursor
water

Total
thickness
effect158.8 nmDeposition
temperatureeffect150 ºCBest conditions:➢ AlOx/TiOy:0.3/0.7➢ Water precursor➢ 250 ºC
➢ Thick filmk➢ Thin film Cmax

Experimental and Results

Fabrication of nanolaminate/diamond MOSFETs

H-diamond

Mesa-structure

Ohmic contact

Nanolaminate

Gate metal

Windows open

Diamond (100)Diamond (100)Diamond (100)Diamond (100)Diamond (100)Diamond (100)

(a)

(b)

(c)

(d)

(e)

(f)

MPCVD
CCP-RIE
Tem.: 900-940 ºC Tem.: RT
Press.: 80 Torr
Press.: 10 Torr
H2 : 500 sccm
O2 : 100 sccm
CH4 : 0.5 sccm
Time: 1.5 min
Time: 1.5-2 hrs
Plasma: 50W
Th.: 150-200 nm

E-gun Evaporator
Press.:10-5 Pa

Pd: 10 nm
Ti: 20 nm
Au: 100 nm

ALD
Prec.: TMA,
TDMAT, waterTem.: 250 ºC
0.7nmTiOy/0.3nm AlOxTotal th.: 57.5nm
AlOx buffer:5 nm

E-gun Evaporator CCP-RIE
Press.:10-5 Pa
Ti: 10 nm
Au: 150 nm

Tem.: RTPress.: 10 Torr
O2 : 100 sccm
Plasma: 50W

Experimental and Results

AlOx/TiOy nanolaminate/AlOx buffer layer/H-diamond MOS capacitor
Liu, et al. Carbon 172, 112 (2021).