Nanolithography for the Nanotech Lab Budget
The semiconductor industry uses nanolithography to etch nano-sized patterns on silicon wafers coated with a material called photoresist. Those patterns make up the circuits on the chip and include nano-sized structures. To create nano-sized features for integrated circuits on silicon wafers requires a machine called a stepper.
Steppers are built to be used in high-volume manufacturing lines, so they have to process more than 100 wafers an hour and run all day, seven days a week, with minimal downtime for maintenance. A machine capable of this type of resolution, as well as low defect levels and low downtime, costs more than ten million dollars.
But, if you are a nanotech researcher, you probably don’t have ten million dollars to invest in a high-volume stepper. If you’re in the market for a low-volume lithography system for your lab, you might try a system that uses dip-pen nanolithography.
These systems are modified from atomic force microscope (AFM) systems that either obtain images of a surface or deposit ink on that surface. The tip is coated with the ink, and ink is deposited where the tip touches the surface.
The ink can be deposited in patterns as fine as 15 nm wide. The width of the pattern depends on how long you leave the tip stationary on the surface; a longer time resting on the surface results in more ink deposited in a wider pattern.
Dip-pen nanolithography systems are useful for making prototypes of nanoscale structures. For example, if you want to see if a molecule will attach to certain other chemical or biological molecules, just coat the substrate with a substance that the first molecule will bond to, for example, gold. Then use the dip pen to deposit the first molecule in an array of dots.
After you create the array, you can expose it to the other molecule and then scan the array with an AFM. If an extra molecule is attached, you’ve succeeded.