Chemistry

Resisting Dendrimers

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Science  30 Apr 2004:
Vol. 304, Issue 5671, pp. 651-653
DOI: 10.1126/science.304.5671.651e

Scanning probe methods have found increasing use for lithographic patterning because of the ability to pattern at tens of nanometers resolution and to align overlayers with similar accuracy, and because the equipment is relatively inexpensive and easy to set up. As with many lithographic methods, a resist, consisting of a thin layer of organic molecules, is used to aid in the selective patterning of the substrate, which is then developed using a chemical etching stage. However, a problem arises for titanium films because the metal and its oxide tend to have similar removal rates when exposed to strong etchants.

Drawing on the success in using dendrimers to enhance silicon lithography, Rolandi et al. have modified the chemistry of the dendrimer's focal point to make it compatible with titanium surfaces. The resist can be used for either positive or negative image transfers. In positive tone mode, the tip of the atomic force microscope (AFM) is used to scrape away selected dendrimer molecules, leading to a faster etching in these exposed areas. For negative tone patterning, a voltage bias is applied across the AFM tip, causing an oxidation of the dendrimer in the selected regions. The writing oxidizes the titanium and degrades the dendrimers, leading to deposition of amorphous carbon, which is very resistant to the etching solution. — MSL

Nano Lett. 10.1021/nl049700i (2004).

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