1. A New Phase in Imaging Finding the odd atom
by Jason Han and Michael Kemeny

2. Hitchhiker’s Guide to Our Presentation
Aims and Introduction to Phase Imaging
Semiconductors
Quantum theory
Transmission Electron Microscope
Phase Extraction using TEM
Data Preparation and Errors
The Results
Jason
Michael

3. Semiconductors and Phase Imaging
Project partially funded by
Semiconductor industry is highly interested in viewing dopant profiles at extremely high resolutions for:
device evaluation
control of production process
Current techniques that allow this heavily involve Phase Imaging

4. Phase Retrieval and Holography
Standard Sine Waveform

5. Phase Retrieval and Holography
Phase can be found by electron holography / interferometry
- Special technical requirements
- Limited field of view
- Phase retrieval using Transmission Electron Microscopy is much more flexible
-Easily extends to many other areas including biological TEM

6. Transmission Electron Microscope
Biofilter TEM

7. Semiconductors
Silicon is typically used for chips and semiconductor devices
Impurities are deposited in extremely small concentrations

8. Semiconductors - Semiconductors have a band structure
-The introduction of dopants adds extra energy levels into gap

9. CMOS and Field-Effect Transistors
Complementary Metal-Oxide
Semiconductor
Metal-Oxide-Semiconductor
Field-Effect Transistor
Source
Drain
Distribution of dopants in a transistor gate
Used in Microprocessors, SRAM and other digital logic circuits.
CMOS devices use much less power than other devices
Terminals in Field-Effect Transistor are called gate, source and drain
Typically made from SiO2

10. Wave Particle Duality of Electrons
- Bohr’s Principle of Complementarity: an electron may behave as a particle or a wave in different circumstances, but never as both simultaneously
The de Broglie equation (1923) assigns a wavelength to an electron

11. Rayleigh Criterion
- The Rayleigh criterion shows that resolution is proportional to wavelength
- Visible light has a wavelength of 400 – 700 nm.

12. An Overview of the TEM

13. Using the TEM
Top right : Sample holder
Above : Michael studying sample
Left : Viewing Hole
- Vacuum leaks may occur during insertion of specimen holder.

14. Aberrations and alignments
- Diffraction patterns (Kikuchi lines) can be used to ensure sample is correctly aligned
- The GIF filters out non-elastic electrons
Above : Diffraction Pattern
Top Right : Tim fiddling with knobs
Right : Fluorescent Screen

15. What does phase represent?
Normal TEM Imaging (Amplitude based) shows:
- Mass-Thickness contrast
- Diffraction contrast
Phase contrast highlights:
- Magnetic fields
- Electrostatic fields
- Topography
Doping changes internal electric fields
Electrostatic potentials can be viewed by Phase Imaging

16. Extracting the Phase Under focus Sample Objective Lens Focal Plane
In Focus
Over focus

17. Extracting the Phase Transport of Intensity Equation:
Probability current is conserved between planes
Phase map (thickness profile)

18. - Beam instability during data acquisition
Cleaning up the mess
MgO Crystal
Underfocus In Focus Overfocus
Phase Map
High Band Pass Filtered Image
FFT Masking
- Alignment
- Beam instability during data acquisition

19. The Results
Silicon based transistor – source and drain region

20. The Results
Section of Junction in Silicon Transistor

21. The Results
Phosphorus Dopants

22. Comparing and Evaluating
Phase image showing contrast in doped regions (A.C. Twitchett and P.A. Midgley)
Phase image of transistors revealing souce and drain areas. (W.D. Rau et al.)
Holographically reconstructed phase image of cross section of a field effect transistor. (H. Lichte)
Our results of cross-section transistor phase image.

23. Conclusions and Consequences
Semiconductors are doped with extremely small impurities and are used to make many modern electronic components
Production needs control of accurate doping to nanometre scales
Phase retrieval methods in Transmission Electron Microscopy is a promising technique to analyse semiconductor devices and help with accurate production
The area still needs much more development, including resolving errors to do with contrast and Fourier transforms
Combine or confirm results with other techniques such as off-axis electron holography
Current research for Intel may result in such possibilities as correcting chip malfunctions, more efficient doping and consequently the next generation of semiconductor devices

24. Acknowledgements
Lichte H. The Royal Society (March 2002), Electron Interference : Mystery and Reality, 360, 897 – 920.
McMahon P.J., Barone-Nugent E.D., Allman B.E., Journal of Microscopy (June 2002) Quantitative phase-amplitude microscopy II: Differential interference contrast imaging for biological TEM. pp
Nagayama K. and Danev R., Asia/Pacific Microscopy and Analysis (July 2003) Image Enhancement with Phase Plates in Electron-Phase Microscopy.
MacCartney M.R. et al. Applied Physics Letters (April 2002), Quantitative analysis of one-deminesional dopant profile by electron holography 80: – 3215
Rau W.D., Schwander P., Ourmazd A.,Phys. Stat. Sol. (March 2000) Two-Dimensional mapping of pn Junctions by Electron Holography
We would like to thank Tim Petersen and Vicki Keast for all their input!