Low temperature deposition of silicon nitride thin films by hot-wire CVD

Low temperature deposition of silicon nitride thin films by hot-wire CVD

Energy Postgraduate Conference 2013

University of the Western CapeUniversity of the Western Cape

A. Adams and C. J. Arendse

Outline• Introduction

• Experimental Details

• Results

• Conclusion

• Acknowledgments

Introduction• Solar power

– Energy crises– Viable alternative– Amorphous solar cells – Antireflective coating for increased efficiency

• Multitude of uses stemming from stoichiometric tunability– Permeation barrier– Gate insulator in thin film electronics– Passivation of dangling bonds– Antireflective coating

Deposition Method• Current technique of choice is PECVD

– Ion bombardment, resulting in oxidation– Complex (potential difference, plasma source)

• Desired technique of choice is HWCVD– Ease of upscale– Eradicates bombardment (absence of plasma ions)

– Low cost– High deposition rates of > 7 nm/s– Low temperature deposition

Experimental details

Technique Information

Reflectance

·         Thickness

·         Band Gap

·         Refractive index

FTIR

·         SiN bonds

·         Total bonded H

EDS ·         N/Si ratio

AFM

·         Surface morphology

·         Roughness

ERDA·         H depth profiling

TOF-HIERD

·         N depth profiling

·         N/Si ratio

XRD ·         Phase

• The a-SiN:H thin films were deposited at Tw=1400 °C, Ts = 240 °C, P = 100 µbar, ΦH2 = 20 sccm, ΦSiH4 = 5 sccm and ΦNH3 = 1 – 7 sccm (LOW PARAMETERS)

Results and discussion• Decrease in deposition rate as ΦNH3 is

increased• Competing reaction at the filament

• Decrease in surface roughness as ΦNH3 is increased

• columnar structures decreases

Results and Discussion• Films are uniform• Negligible oxidation occurred in the bulk • Increase in N content as NH3 is increased

• ToF-HIERD and EDS corroborate well

NH3 = 5 sccm

Results and Discussion

Results and discussion• Linear relation between static refractive

index and N content• Direct relation between Tauc band gap

and N content

Conclusion

• High quality a-SiN:H deposited at low processing parameters, suitable for device applications (permeation barrier, Passivation layer)

• Resistant to oxidation• Tuneable refractive index• Corroboration between EDS, ToF-HIERD• Low H content• Silicon rich Films

Future Work• Incorporation in organic PV devices

Acknowledgments

• Financial Support− University of the Western Cape− National Research Foundation (NRF)

• Team‒ A. Adams, Prof. C. Arendse, Dr. T. F. G. Muller, Dr. G. Malgas, Dr. C. Oliphant and

Dr. M. Msimanga.