1. Scanning Probe Lithography
Yongshik Park
February 13th, 2008
EE C235/NSE C203

2. Outline Scanned Probe Oxidation
Generating an Polymer “Resist” Layer using Scanning Probe Lithography
High-Field Scanning Probe Lithography in Hexadecane
Cons and Pros
Conclusions

3. Scanned Probe Oxidation
Began at NIST in 1989
Electrical bias between a conducting tip and a substrate induces a highly localized enhanced oxidation.
Typical line width: 10~20nm
J. A. Dagata, Science, Vol. 270, 1995, pp

4. Scanned Probe Oxidation- Applications
Fabrication of
single tunneling transistor(SET)
Fabrication of Si nanowire
J. A. Dagata, Science, Vol. 270, 1995, pp

5. Generating an Etch Resistant “Resist” Layer from Common Solvents
Fluid Cell
DC Bias
Solvent vapor
An organic electrolyte replaces water to generate an organic resist.
Scan rate: 10um~20um
I. Suez, S. Backer, J. Frechet, Nano Letter, Vol. 5, No. 2, 2005, pp

6. Generating an Etch Resistant “Resist” Layer from Common Solvents
After generating n-octane patterns
After etching
The height of n-octane: 2.5nm (40% higher than the case of water)
After etching, the height of step: 8.5nm
I. Suez, S. Backer, J. Frechet, Nano Letter, Vol. 5, No. 2, 2005, pp

7. High-Field Scanning Probe Lithography in Hexadecane - Hydrophobocity
Surface hydrophobocity determines the deposited material.
Hydrophilic  SiO2
Hydrophobic  n-octane
Oxidation of the silicon surface occurs in the meniscus formed by the water dissolved in the fluid, with minimal effects on the reaction from the surrounding solvents
I. Suez, M. Rolandi, S. Backer, A. Scholl, J. Frechet, Advanced Materials, Vol. 19, 2007, pp

8. High-Field Scanning Probe Lithography in Hexadecane - Hydrophobocity
After deposition(black)
After etching(red)
On Hydrophilic surface
On Hydrophobic surface
Etching makes trenches on hydrophilic surface and tall posts on hydrophobic surface.
I. Suez, M. Rolandi, S. Backer, A. Scholl, J. Frechet, Advanced Materials, Vol. 19, 2007, pp

9. High-Field Scanning Probe Lithography in Hexadecane – PEEM analysis
AFM image
Carbon signal PEEM
PEEM analysis
Although there are only small differences in features of the local spectra, carbon content information was obtained
1st and 2nd peak: C=C double bond
3rd peak: hybridized carbon atoms
I. Suez, M. Rolandi, S. Backer, A. Scholl, J. Frechet, Advanced Materials, Vol. 19, 2007, pp

10. Cons and Pros
Cons
Can make nano patterns without optical apparatus
Can control deposited material by hydrophobocity of the surface
Can make arbitrary patterns by controlling the trajectory of AFM tip
Pros
Low throughput: serial scan and low speed
Multiple tips
Small scan area

11. Conclusions Scanning probe oxidation can make nanowire, SET, etc.
By using an organic solvent, the organic material can be deposited on the surface.
The hydrophobocity determines the deposited material
Hydrophilic surface  SiO2
Hydrophobic surface  hydrocarbon
By PEEM analysis, the deposited material on the hydrophobic surface has carbon components.