Fabrication of Largearea Ultrafine Periodic Nanostructures with Multilayer Processing

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Fabrication of Large-area Ultra-fine Periodic
Nanostructures with Multilayer Processing

• Chih-Hao Chang, Yong Zhao, Ralf K. Heilmann,
• and Mark L. Schattenburg
• Space Nanotechnology Laboratory

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Periodic Nanostructures
(Minseung Ahn, SNL)
Magnetic media (2D)
C. A. Ross et al., J. Appl. Phys., 91 (10), 2002
Template for self-assembly (1D)
J. Y. Cheng et al., App. Phys. Lett., 81 (19),
2002
Diffraction grating (1D)
Photonic crystal (3D)
M. Qi et al., Nature, 429, 2002
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Nanoruler
A small beam makes a small interference pattern,
which is scanned.
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Overlay Issues
Spatial-phase locked EBL
Align pattern on mask
Nanoruler Reading mode
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Spatial-frequency Multiplication
Reference layer
Grating layer 1
Grating layer 2
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Duty-cycle Binary Resist Model
Positive resist
Negative resist

• Duty cycle gt 0.875 required for 4X.
• Negative resist desirable, but acid diffusion
  limits duty cycle.
• Positive resist with image reversal techniques.

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Image Reversal with Positive Resist
(a) Overexpose positive resist for duty-cycle lt
0.5.
(d) O2 RIE.
(b) Spin silicon-containing polymer.
(d) CHF3 RIE, resulting in duty-cycle gt 0.5.
Si-containing polymer
Resist
(c) CF4 RIE.

• Material from Molecular Imprint for Nanoimprint.

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Phase Overlay
0 phase offset
? phase offset
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Phase Overlay Error Map

• Auto-imaging with Raith 11x10 images

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Spatial-frequency Doubling
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Future work

• Improve linewidth control
• Lithography
• Processing
• Trim resist lines with isotropic etch (PE).
• Simulate efficiency vs phase offset.
• Convert Nanoruler to 200 nm period.
• Goal 4x exposure at 200 nm to make 50 nm period.
• Think about 6x 8x.