A new nanolithography process promises to speed up the “printing” of nanoscale patterns, which could soon allow investigators to quickly make prototypes of test electronic devices.
Of course, various forms of fairly high resolution nanolithography have been around for a while. But, heretofore, they have been relatively time consuming. These have usually employed a single “pen” that slowly deposits materials on a substrate.
Now, however, according to a Northwestern University press release, researchers have come up with a method of using an array of millions of tiny light-beam pens on photosensitive material that can operate simultaneously. It is essentially massively parallel scanning probe microscopy that can create any pattern by shining 400-nanometer light through nanoscopic apertures at each pen tip in the array.
Details of the “beam-pen lithography” method appear in a letter published in Nature Nanotechnology. According to the authors, beam-pen lithography might do for nanofabrication what the desktop printer has done for printing and information transfer.
“It’s all about miniaturization,” says Chad Mirkin, director of Northwestern University’s International Institute for Nanotechnology. “Rapid and large-scale transfer of information drives the world. But conventional micro- and nanofabrication tools for making structures are very expensive. We are trying to change that with this new approach to photolithography and nanopatterning.”
To demonstrate some of the power of beam-pen lithography, Mirkin’s group patterned 15,000 replicas of the Chicago skyline simultaneously. The demonstration used fifteen thousand tiny pens to create the skylines over square centimeters of space. Each skyline pattern is made up of 182 dots, with each dot approximately 500 nanometers in diameter. It took 20 seconds of light exposure to create each dot in the photosensitive material.
Resolution-wise, the method can toggle between near- and far-field distances, allowing both subdiffraction limit (100 nanometer) and larger features to be generated. They also say that since their paper was accepted by the journal, they have learned how to create an array of 11 million pens in an area only a few centimeters square.
“Such an instrument would allow researchers at universities and in the electronics industry around the world to rapidly prototype-and possibly produce-high-resolution electronic devices and systems right in the lab. They want to test their patterns immediately, not have to wait for a third-party to produce prototypes, which is what happens now,” Mirkin says.
The pens, themselves, are tiny polymer pyramids. The news release says the pyramids’ points serve as the printing tips:
The researchers coat the pyramids with a very thin layer of gold and then remove a tiny amount of gold from each tip. The large open tops of the pyramids (the back side of the array) are exposed to light, and the gold-plated pyramids channel the light to the tips. A fine beam of light comes from each tip, where the gold was removed, exposing the light-sensitive material at each point
“Another advantage is that we don’t have to use all the pens at once. We can shut some off and turn on others,” says Mirkin. “Because the tops of the pyramids are on the microscale, we can control each individual tip.”
Mirkin’s history suggests that this technique may be a big success. He developed two other commercially successful lithography techniques: polymer-pen lithography in 2008 and dip-pen nanolithography in 1999.