Dendrimer Monolayers As Negative & Positive Tone Resists For Scanning Probe LithographyMarco Rolandi, Itai Suez, Hongjie Dai, Jean M. J. Frechet

UC Berkeley, L.B.L. and Stanford

NANO LETTERS. 2004 Vol. 4, No. 5 889-893

Presented by Liang Pan

Many things need to be improved including resists

Limitation of Conventional Resist for sub-10nm resolution

Chemical amplification help to increase the sensitivity (need fewer photons to initiate reaction), but resolution of most of conventional PR is limited by diffusion process of radical reactions.

Example*: Deprotection scheme.

This PR was used for DRAMs fabrications in IBM.

* IBM J of R&D. Volume 41, Numbers 1/2, 1997 Optical lithography

New Scheme using Monolayer Resist Monolayer resist by self-

assembly techniques. Provides nanometer thick

and uniform resist layer over large area

Good etching resistance Photon/Electron harvesting

structure Greatly increases sensitivity

without diffusion process

Monolayer by self-assembly

Light-harvesting structure*

* M. Oar et al. Chem. Mater. 2006, 18, 3682-3692

Dendrimer Monolayers Structures*

* M. Rolandi et al. NANO LETTERS. 2004 Vol. 4, No. 5 889-893

Dendrimer MoleculesIt takes about 30 minutes for the self-assembly process to finish in solution

Anchor

Antenna

SPL ProcessUsing (not limited by) AFM

* M. Rolandi et al. NANO LETTERS. 2004 Vol. 4, No. 5 889-893

Lithography Results

Positive Tone Negative Tone

* M. Rolandi et al. NANO LETTERS. 2004 Vol. 4, No. 5 889-893

Related Works* about Self-Assembly Patterns

In another work, they broke down some bonds using AFM, and then selectively assembled different end-groups to do self-assembly lithography.

* S. Backer et al. Langmuir 2007, 23, 2297-2299

Assembly Results

After exposing to end-groups solution for 12~24 h in a dry nitrogen environment, etching masks were generated by self-assembly.

* S. Backer et al. Langmuir 2007, 23, 2297-2299

Summary The authors have devised new scanning probe

lithography schemes based on a self-assembled monolayer resists.

They demonstrated formation of both negative and positive tone pattern transfer.

Currently, only 20nm resolutions were demonstrated due to the limitation of AFM tips sharpness.

They claimed that dendrimer resists is possible to push lithographic resolution to a few nanometers.

Thank you!

Questions?