Characterization of ALD Gate Oxide Films Via Electrical Measurements, Wet Etch, and Other

Techniques_______________________________________________________________________________

Karlie C. McDaniel

2018 NNCI REU Convocation Raleigh, NC

August 5-8, 2018

Center for Nanoscale SystemsMentor: Mac Hathaway

Harvard UniversityCambridge, MA

Acknowledgements

• PI: Jiangdong Deng• Mentor: Mac Hathaway

• CNS Staff/Facility • Harvard SEAS • NNCI for funding

Purpose

Advanced characterization of ALD (atomic layer deposition) oxide films for enhanced application to user requirements.

_____________________________________________________________________________________________________

Research Outline

• Depositing a variety of oxides onto silicon wafers at 100C - 240C with the ALD• Deposition materials include: Al2O3

HfO2 TiO2 ZrO2 SiO2

• Wet etch rate from 100:1 HF >>> Film Density• Ellipsometer measurement >>> Film Thickness • Electrical testing with eGain liquid metal probe >>> Electrical Breakdown Voltage • FTIR Spectroscopy>>> OH content

Atomic Layer Deposition

• ALD 1 and ALD 4 usage• Low to mid range temperature range (100 -250 C) • Single atomic monolayers• High Uniformity• Extreme Conformality • Slow deposition rates• Alternates gas pulses

Ellipsometry

• Measures changes in light polarization to determine the samples material properties.1) Film thickness2) Optical Constants

• Data analysis• Mean squared error (MSE), is used to quantify

differences between curves.

Work Flow

ALD Ellipsometry Wet Bench

FTIReGain Probe

0

0.5

1

1.5

2

2.5

0 50 100 150 200 250 300

Aver

age

Etch

Rat

es (A

/s)

ALD Growth Temperature (C)

Wet Etch Rates in 100:1 HF

Etch Rate (HfO2)

Etch Rate (TiO2)

Etch Rate (ZrO2)

0

0.5

1

1.5

2

2.5

3

3.5

0 50 100 150 200 250 300

Aver

age

Etch

Rat

e (A

/s)

ALD Growth Temperature (C)

Wet Etch Rates in 100:1 HF

Etch Rate (HfO2)

Etch Rate (TiO2)

Etch Rate (ZrO2)

0

1

2

3

4

5

6

7

8

9

0 50 100 150 200 250 300

Aver

age

Etch

Rat

e (A

/s)

ALD Growth Temperature (C)

Wet Etch Rates in 100:1 HF

Etch Rate (Al2O3)

Etch Rate (HfO2)

Etch Rate (SiO2)

Etch Rate (TiO2)

Etch Rate (ZrO2)

0

1

2

3

4

5

6

7

8

9

0 50 100 150 200 250 300

Aver

age

Etch

Rat

e (A

/s)

ALD Growth Temperature (C)

Wet Etch Rates in 100:1 HF

Etch Rate (Al2O3)

Etch Rate (HfO2)

Etch Rate (SiO2)

Etch Rate (TiO2)

Etch Rate (ZrO2)

FTIR Absorption Spectrum of Al2O3 and HfO2 vs Deposition Temp.

OH Region

____ 100C Al2O3

____ 240C Al2O3

OH Region ___ 100CHfO2

Electrical Characteristics

0

20

40

60

80

100

120

140

0 50 100 150 200 250 300

Brea

kdow

n Vo

ltage

(V/n

m)

ALD Growth Temperature (C)

Breakdown vs Deposition Temperature

Al2O3

HfO2

Ongoing Work

• Exploring the behavior of etched films with regard to breakdown.• Confirming the correlation of OH content with etch rate variation

- Using repeated samples- Atom Probe Tomography

• Looking at the behavior of nanolaminates.

Thank You