Credit: © 2010 AAAS

The semiconductor industry uses masks to write patterns onto substrates at many stages during device fabrication. Masks are commonly made from organic resist materials because they are amenable to patterning. However, standard optical and electron beam lithography techniques struggle to produce mask feature sizes below 30 nm. Now, Armin Knoll and colleagues at IBM Research centres in Zurich, San Jose and Yorktown Heights have used a scanning probe to pattern resists to a resolution of 15 nm at high speeds and in three dimensions (Science 328, 732–735; 2010).

The method involves applying a controlled amount of heat and pressure to a glassy organic resist through a scanning probe tip, overcoming the weak hydrogen bonds that bind the resist molecules and causing the resist to evaporate. Previous 'heated tip' methods involved breaking covalent bonds or causing chemical changes, which made them slow and also led to contamination of the tip. The new approach allows a resolution of 15 nm to be achieved at speeds comparable to electron beam lithography, which are sufficient for rapid prototyping. Higher speeds could be reached by using many scanning probes simultaneously.

The technique can also produce three-dimensional patterns by successively scanning over the same area of resist, removing varying depths with each scan. The IBM team used this approach to construct a 25-nm-high replica of the Swiss mountain, the Matterhorn. This shape (pictured) was subsequently etched into a silicon wafer.