MIT.nano: engineering at the heart of the Institute

Scholvin: “Nothing that happens in microfabrication should work. And the reason it’s possible is because we negotiate with nature, in some sense.”

Jorg Scholvin can distinguish silicon materials just two nanometers apart in thickness with his naked eye. In the blanched rooms of Building 12, machines buzz a steady low hum. The MIT.nano veteran points out three thin, circular plates of varying colors on a metal table. The brownish-orange one, he says, is coated in a film 60 nanometers (nm) thick. The purple one corresponds to 68 nm, and light blue to 72 nm. “There are tools that can tell me this,” Dr. Scholvin ’00 PhD ’06 states from behind his cleanroom suit mask, but “I know from the color.”

These plates are 200-millimeter (8 inches in diameter) wafers, thin slices of semiconductor such as silicon. They are commonly used in industry as a base for etching and deposition to create microcircuits, solar cells, and other devices. MIT.nano houses instruments used in industry, as well as those geared specifically towards research. 

The physics is simple enough: light waves travel down and either reflect off of the top surface of film or continue down through it, reflecting on the bottom surface. The light that our eyes see is a combination of the two waves, and the different colors are a result of the waves interfering with each other. The blue 72 nm wafer, for instance, indicates that light rays are constructively interfering in the blue range, whereas red and green wavelengths are destructively interfering. Oil spills and soap bubbles, with their rainbow patterns, display the same phenomenon, called thin film interference.

Scholvin presents a fourth wafer, colored somewhere in between the purple and light blue ones, which means it has a film thickness of around 70 nm. For reference, a strand of hair is about 100,000 nanometers thick. This means that the difference between these plates is as little as two nanometers, or 10 layers of silicon nitride – and it is easily observable to the naked eye. “This shouldn’t be possible,” Scholvin states. It is still baffling, even after his years of experience.

These technologies are not only possible but accessible for MIT and external groups.

Around 500-600 users have their primary projects in the nanofabrication lab (“the fab” for short), but there are even more who temporarily use the technologies for a larger project. Start-ups and over 40 labs on campus come in for applications ranging from coating a stainless steel needle with nanoparticles for biomedical inventions, to creating nanoscale filters for corrosive liquids in order to recycle batteries. “Those are fun things because they are the non-obvious applications of the fab,” Scholvin states, “and they enable something that otherwise wouldn't be possible.” Being conveniently situated in the center of campus means that “everyone is within pretty much a 3-minute walk of the lab.”

Scholvin stated that users range from 17 to 70 years in age. As early as freshman year, MIT students can take the IAP workshop “Make your own chip inside the lab!” or the intro class Micro/Nano Processing Technology (6.2600[J]). Students from almost every course have taken a class in the fab.

One motivation of these classes and workshops is to introduce underclassmen to nanofabrication and its vast applications early on. Scholvin reflects on his experience as an undergraduate at MIT studying electrical engineering. Like many, he delayed taking the GIR biology class until his senior year. “I was sitting in class like, ‘Wow! This is kind of cool.’ But, too late! If I had taken it earlier, maybe I could have mixed it with something else,” he shares. “If you're a sophomore or freshman, ideally, you get exposed to this environment and that gives you the chance to say, ‘This is something I want to do.’”

Scholvin believes that all it takes is to be in a space for a short amount of time, to know that something exists. “In the fabrication world,” he states, “you can contribute and do cutting edge parts relatively quickly.”

The mysteries of nanofabrication are endless. “Nothing that happens in microfabrication should work,” Scholvin argues. “And the reason it's possible is because we negotiate with nature, in some sense.”

Say someone wants to be able to fly. It’s not possible, unless they use an airplane. “You give up on generality, but ideally the things you give up will allow you to do it,” Scholvin explains. Similar concessions are made in the negotiation of nanotechnologies.

“That's what goes on in the lab. How do you take something that, at first glance, is impossible to do, and find the right boundary conditions and the right constraints so suddenly it becomes possible?” It may be as simple as spacing devices out a certain amount, or having them face the same direction, or it may be a more complex puzzle.

The colored silicon wafers are an example of this. The human eye generally cannot see the difference of a few atoms, but in this case, it is possible – on thin films only. This is a generality that is negotiated for this ability to distinguish between a 68 nm film and a 70 nm film.

“It is beautiful,” Scholvin states. “That is impressive.”