Electron Exposure of Resist. One scheme for performing lithography with scanning probes involves the electron exposure of a resist material, such as an organic polymer or a monolayer resist. When a conducting tip is biased negatively with respect to a sample, electrons are field-emitted from the tip. If a sample is coated with a thin resist, the emitted electrons traverse the resist. The resist absorbs energy from the electron radiation, which induces chemical changes in the resist. For organic polymer resists, the radiation scissions bonds (positive resist) or crosslinks molecules (negative resist). As a result, when the resist is submersed in a special solvent (the developer), only the irradiated areas dissolve (for positive resists; opposite for negative resists).The resist pattern can then be transferred to the substrate using selective chemical etching or dry etching or through lift-off.

Advantages of Exposure Lithography with Scanning Probes. Organic polymer resists provide an attractive option for SPL because many have a low threshold voltage, high sensitivity, sub-100-nm resolution, and good dry etch resistance. Moreover, these resists can be easily deposited on virtually any substrate, and many organic polymers are well characterized from use in photolithography or e-beam lithography. It is also possible to pattern at high speeds with this method. Finally, the polymer surface is soft and pliable which minimizes the tip wear. We have made advances in the increasing both the reliability and the throughput of resist exposure by scanning probes.

exposure of resists....

............hybrid afm/stm lithography