EFFECT OF REACTION PARAMETERS ON EXERGY EFFICIENCY OF ATOMIC LAYER DEPOSITION Al2O3 FILMFenfen Wang, Chris YuanDepartment of Mechanical Engineering, UWM

Understand and improve the energy efficiency of Atomic Layer Deposition (ALD) nanotechnology from a hierarchical systems perspective.

Research Object: ALD of Al2O3 thin film process

·Establish mathematical modeling of exergy (energy) flow and exergy efficiency of ALD process

·Get a better understanding of the effects of reaction parameters on exergy efficiency of ALD process

Optimize ALD technology for the improvement of its energy utilization, thus paving the way for its furture large-scale sustainable applications.

Exergy

Definition: The maximum work obtainable when some matter is brought to a state of thermodynamic equilibrium with the reference environment by means of reversible processes.

Reference temperature (T0): 298.15 K Reference pressure (p0): 1 atm.

Exergy analysis method

Combining the first and second laws of thermodynamics

• Objective:

To identify sites where exergy losses occur and rank order them for significance for the analysis, design and improvement of systems.

• Importance:

Allowing attention to be centered on the aspects of system operation that offer the greatest opportunity for improvement.

Firstly, three kinds of exergy efficiency are calculated by changing reaction parameters (N2 flow rate, reaction temperature and purging time)

Then, further analyses of effects of reaction temperature and purging time on exergy efficiency are conducted.

• [1] George, S. M., Atomic layer deposition: an overview. Chemical reviews, 110 (1), 111-131, 2009.

• [2] Yuan, C., Dornfeld, D., Environmental performance characterization of atomic layer deposition. Proceedings of IEEE International Symposium on Electronics and the Environment, San Francisco, California.

• [3] Renaldi, Karel Kellens, Wim Dewulf, Joost R. Duflou, Exergy Efficiency Definitions for Manufacturing Processes. Springer, 329-334, 2011.

OBJECTIVES METHODOLOGY RESULTS (Cont.)

Effect of reaction parameters on exergy efficiencies of Atomic layer deposition (ALD) of Al2O3 thin film is studied.

N2 flow rate has little effect on exergy efficiency. Exergy efficiencies decrease with the increase of both temperature and purging time.

Reducing reaction temperature and purging time to a certain degree can improve energy efficiency of ALD process.

This research paves the way for future optimization for the improvement of energy utilization and sustainability performance of ALD technology.

CONCLUSION

BIBLIOGRAPHY

• Fenfen Wang, Email: fenfen@uwm.edu

• Chris Yuan, Email: cyuan@uwm.edu

CONTACT INFORMATION

Results

N2 flow rate has little effect on all exergy efficiencies.

Reaction temperature and purging time have relatively big influences on exergy efficiencies.

Maximum exergy efficiencies are obtained at:• purging time is equal to 4 s (N2 flow rate and reaction temperature are constant)

• Reaction temperature is equal to 423K (N2 flow rate and purging time are constant)

ACKNOWLEDGEMENT

• This study is financially supported by the National Science Foundation (NSF U.S. Grant No. CMMI-1200940)

ex

u

p

Exergy efficiencies decrease with the increase of both temperature and purging time.

Purging time has more influence on exergy efficiencies than temperature does.

Exergy efficiencies under different reaction parameters

Sustainability issues about ALD technology

• Heavy wastes of toxic chemicals• Nano-particle emissions• high material and energy consumptions

Nano particle emissions

Energy consumption of 300 cycle ALD processes at 473 K [2]

Waf

er p

retre

atm

ent

Pulsing T

MA

Pulsing H

2O

System

contro

l

Pipeli

ne hea

ting

Annealin

g0

200

400

600

800

1000 Computer

Electronics

Compressed air

Pumping

Heating

ener

gy c

onsu

mp

tion

(K

J)

B

Physical exergy Bph

Chemical Exergy Bch

Material flow exergy

BW=W

Work flow exergy

BQ=(1-T0/T)Q

Heat flow exergy

System State

Reference State

Exergy=Maximum work attainable by returning the system from the System State to the Reference

State

Exergy (B)

Bin

(1-T0/T)Qin

Win

Bout

(1-T0/T)Qout

Wout

Exergy flow in a system [3]

Transiting exergy in the useful output stream Btr,u

Exergy outputBout

Transiting exergy in the input stream Btr,in

Exergy inputBin

Internal exergy lossessBloss,int External Exergy

LossessBloss,ext

Transiting exergy in the losses stream Btr,loss

Useful Exergy outputBu

Exergy efficiency under different reaction temperatures

Exergy efficiency under different reaction temperatures

Introduction

Importance of ALD technology [1]:

Semiconductors90nm 45nm

Atomic layer growth of thin films

Diffusion

Adsorption

Reaction

Dissociation

Dielectric miniaturization

SampleChannel

gatedrainsource

Need for high k dielectric films

Channel

drain

Dielectric layer

source

Deposition mechanism of ALD Al2O3

3 3 2 2 3 42Al(CH ) 3H O Al O 6CH* *

3 3 3 2 4Al OH Al(CH ) Al O Al(CH ) CH * *

3 2 4Al CH H O Al OH CH

ALD of Al2O3 cycles

CH4

TMA

CH3 surface

OH surface CH4

N2

Purge

Purge

H2ORepeat TMA

Cambridge Nanotech SavannahALD of Al2O3 cycles S100 ALD system

chamber

Carrier gas line

Vacuum valve

manifold

Precursor cylinderStop valve

ReactionsN2 flow rate

(sccm)Reaction

temperature (K)Purging time (s)

1 20 423 4

2 20 473 4

3 20 523 4

4 20 423 8

5 20 473 8

6 20 523 8

7 20 423 12

8 20 473 12

9 20 523 12

10 30 423 4

11 30 473 4

12 30 523 4

13 30 423 8

14 30 473 8

15 30 523 8

16 30 423 12

17 30 473 12

18 30 523 12

19 40 423 4

20 40 473 4

21 40 523 4

22 40 423 8

23 40 473 8

24 40 523 8

25 40 423 12

26 40 473 12

27 40 523 12