K. C. Kragh Dept. of Physics and Optical Engineering, Rose-Hulman - - PowerPoint PPT Presentation

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K. C. Kragh Dept. of Physics and Optical Engineering, Rose-Hulman - - PowerPoint PPT Presentation

Nov 24, 2022 117 likes •367 views

Atomic Layer Deposition of Hafnium Oxide at Temperatures below 100C K. C. Kragh Dept. of Physics and Optical Engineering, Rose-Hulman Institute of Technology REU Student in the Advanced Materials Research Laboratory, University of Illinois

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SLIDE 1

Atomic Layer Deposition of Hafnium Oxide at Temperatures below 100ºC

  • K. C. Kragh
  • Dept. of Physics and Optical Engineering,

Rose-Hulman Institute of Technology REU Student in the Advanced Materials Research Laboratory, University of Illinois – Chicago

Mentors: Dr. G. Jursich and Dr. C. G. Takoudis

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SLIDE 2

Objectives

  • To examine low temperature Atomic Layer

Deposition (ALD) growth of HfO2 on Si

  • To verify the composition of low

temperature HfO2 films

  • To deposit HfO2 on polymer fibers for

creating nanotubes

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SLIDE 3

Thin film layers compose the structures

  • f micro-scale technology.
  • International Nomenclature

– MEMS: Micro Electro Mechanical Systems – MST: Micro Systems Technology

  • Applications to every scientific field

SiO2 Al Ti

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SLIDE 4

Nanoscale thickness of layers requires a separate deposition technique

Oxidizer One Atomic Layer Precursor

Atomic Layer Deposition (ALD)

Hf(N(C2H5)2)4 H2O

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SLIDE 5

Process Overview

  • Control Parameters
  • Substrate Preparation & Insertion
  • Lower the Reactor Pressure
  • Reaction
  • Raise the Reactor Pressure
  • Removal of Substrate
  • Analysis
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SLIDE 6

ALD Reactor

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SLIDE 7

Analysis of Film Thickness

  • Spectral Ellipsometer

– Material Model – Calibrated Reflection – Sample Preserved

  • Low Temperature

Results

– Nonuniformity – Variation in values

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SLIDE 8

Average Thickness after 50 cycles for a 5s Pulse Time with various Reactor Temperatures

50 100 150 200 250 20 40 60 80 100 120 140 160 Reactor Temperature (ºC) Average Thickness (Å)

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SLIDE 9

X-ray Photoelectron Spectroscopy (XPS) identifies elements by binding energy.

Source: 1486.6 eV Al Kα The photon (hf) must overcome – Work Function (φ) – Binding Energy (B.E.) Resulting Data from: B.E. = hf – K.E. – φ Sample Destroyed By Photoemissive Electrons

Image: Simon Garrett http://www.cem.msu.edu/~cem924sg/Topic09.pdf

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SLIDE 10

Examine the Complete Survey

XPS Survey across HfO2 deposited on Silicon at 60ºC

200 400 600 800 1000 Binding Energy (eV)

531 eV O 1s 213 eV and 224 eV Hf 4d5/2 and 4d3/2 381 eV Hf 4p3/2 439 eV Hf 4p1/2 282 eV C 1 s 17eV Hf 4f

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SLIDE 11

Examine the Hf 4f Doublet

062308 Reactor at 60ºC for 5s pulses XPS Hf 4f scan after sputtering

14 16 18 20 22

Binding Energy (eV) Intensity (a.u.)

17.6 eV 19.3 eV

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SLIDE 12

Confirm HfO2 Films at Low Temperatures

  • Peaks are in place
  • 15.8 eV Bulge is Hf-N

Bonding

14 16 18 20 22 Binding Energy (eV) Intensity (a.u.) 30ºC 40ºC 60ºC 70ºC 80ºC

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SLIDE 13

Inorganic nanotubes are the focus of increasing research.

  • PCL Fibers (Poly-

Caprolactone)

  • Hafnia tubes by ALD
  • Applications:

– Electrical – Chemical – Mechanical

Top Image: Berserker79 http://en.wikipedia.org/wiki/Image:Pcl_synthesis.png Right Image: Dr. Alan W. Nicholls & K. C. Kragh

PCL Fibers from Dr. A. Yarin

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SLIDE 14

Cautions & Considerations for Polymer Fibers

  • Temperature Operation
  • Careful Loading
  • Rigid Support
  • Slowly Dropping Pressure
  • Heating Strip Caution
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SLIDE 15

Problems & Concerns

  • Melting Temperature ~ 60ºC

– Aldrich Polycaprolactone (PCL) Beads – Worrisome deposition – Drop to sub-60ºC runs

  • Time Per Run
  • Quality of Fibers
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SLIDE 16

Pressure Variations

  • Worried about Blowing out Fibers
  • Tried Lengthen the Distance

– Tube Temperature Concerns – Deposition Rate Concerns

  • Tried Grating Possibilities
  • Solution: Steel Envelope
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SLIDE 17

Examination of HfO2 Coated Fibers

Scanning Electron Microscope (SEM)

– Scattered Electrons – High Magnification – Composition found by Energy Dispersive X-ray (EDX) – Back-Scattering for relative Atomic Number

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SLIDE 18

Uncoated and Coated PCL Packets

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SLIDE 19

Hafnium Oxide on PCL Fibers by Back-Scattering

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SLIDE 20

EDX Composition of HfO2 PCL Fibers

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SLIDE 21

Conclusions and Future Work

  • ALD growth of HfO2 films will occur down

to room temperature of 30ºC on Si & PCL

  • ALD could be used to create hafnia

nanotubes with polymer heating Future Work: Heat out the PCL to create the actual nanotubes and evaluate their properties

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SLIDE 22

Photo References

  • Garrett, Simon J. 2001. Special Topic in Analytical

Chemistry (CEM 924) Resource Page. http://www.cem.msu.edu/~cem924sg/index.html. Accessed 2008 June 16.

  • Berserker79

http://en.wikipedia.org/wiki/Image:Pcl_synthesis.png

  • All SEM photos captured on the Hitachi S-3000 N

Scanning Electron Microscope operated by Dr. Alan W. Nicholls, Director of Research Service Facility and Electron Microcopy for University of Illinois at Chicago

  • All other figures and graphs from K. C. Kragh
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SLIDE 23

Acknowledgements

  • National Science Foundation (NSF)
  • Department of Defense (DoD)
  • Grants: NSF-EEC 0755115 & NSF-CMS 0829903
  • Professor G. Jursich
  • Professor C. G. Takoudis
  • Professor A. Yarin
  • Dr. Alan W. Nicholls
  • Adam Kueltzo
  • Qian Tao
  • Manish Singh
  • Suman Sinha Ray
  • Lin Jiang