Not stuck on silicon | MIT News

In 2016, annual international semiconductor gross sales reached their highest-ever level, at $339 billion worldwide. In that very same yr, the semiconductor trade spent about $7.2 billion worldwide on wafers that function the substrates for microelectronics parts, which might be was transistors, light-emitting diodes, and different digital and photonic gadgets.

A brand new method developed by MIT engineers might vastly cut back the general value of wafer know-how and allow gadgets produced from extra unique, higher-performing semiconductor supplies than standard silicon.

The brand new methodology, reported immediately in Nature, makes use of graphene — single-atom-thin sheets of graphite — as a kind of “copy machine” to switch intricate crystalline patterns from an underlying semiconductor wafer to a high layer of similar materials.

The engineers labored out fastidiously managed procedures to position single sheets of graphene onto an costly wafer. They then grew semiconducting materials over the graphene layer. They discovered that graphene is skinny sufficient to look electrically invisible, permitting the highest layer to see via the graphene to the underlying crystalline wafer, imprinting its patterns with out being influenced by the graphene.

Graphene can be quite “slippery” and doesn’t have a tendency to stay to different supplies simply, enabling the engineers to easily peel the highest semiconducting layer from the wafer after its constructions have been imprinted.

Jeehwan Kim, the Class of 1947 Profession Improvement Assistant Professor within the departments of Mechanical Engineering and Supplies Science and Engineering, says that in standard semiconductor manufacturing, the wafer, as soon as its crystalline sample is transferred, is so strongly bonded to the semiconductor that it’s nearly unimaginable to separate with out damaging each layers.

“You find yourself having to sacrifice the wafer — it turns into a part of the system,” Kim says.  

With the group’s new method, Kim says producers can now use graphene as an intemediate layer, permitting them to repeat and paste the wafer, separate a copied movie from the wafer, and reuse the wafer many instances over. Along with saving on the price of wafers, Kim says this opens alternatives for exploring extra unique semiconductor supplies.

“The trade has been caught on silicon, and although we’ve recognized about higher performing semiconductors, we haven’t been in a position to make use of them, due to their value,” Kim says. “This provides the trade freedom in selecting semiconductor supplies by efficiency and never value.”

Kim’s analysis crew found this new method at MIT’s Analysis Laboratory of Electronics. Kim’s MIT co-authors are first writer and graduate scholar Yunjo Kim; graduate college students Samuel Cruz, Babatunde Alawode, Chris Heidelberger, Yi Track, and Kuan Qiao; postdocs Kyusang Lee, Shinhyun Choi, and Wei Kong; visiting analysis scholar Chanyeol Choi; Merton C. Flemings-SMA Professor of Supplies Science and Engineering Eugene Fitzgerald; professor {of electrical} engineering and pc science Jing Kong; and assistant professor of mechanical engineering Alexie Kolpak; together with Jared Johnson and Jinwoo Hwang from Ohio State College, and Ibraheem Almansouri of Masdar Institute of Science and Expertise.

Graphene shift

Since graphene’s discovery in 2004, researchers have been investigating its distinctive electrical properties in hopes of enhancing the efficiency and price of digital gadgets. Graphene is an especially good conductor of electrical energy, as electrons circulation via graphene with nearly no friction. Researchers, due to this fact, have been intent on discovering methods to adapt graphene as an inexpensive, high-performance semiconducting materials.

“Folks have been so hopeful that we’d make actually quick digital gadgets from graphene,” Kim says. “But it surely seems it’s actually arduous to make an excellent graphene transistor.”

To ensure that a transistor to work, it should have the ability to flip a circulation of electrons on and off, to generate a sample of ones and zeros, instructing a tool on learn how to perform a set of computations. Because it occurs, it is rather arduous to cease the circulation of electrons via graphene, making it a wonderful conductor however a poor semiconductor.

Kim’s group took a wholly new method to utilizing graphene in semiconductors. As a substitute of specializing in graphene’s electrical properties, the researchers regarded on the materials’s mechanical options.

“We’ve had a powerful perception in graphene, as a result of it’s a very strong, ultrathin, materials and kinds very robust covalent bonding between its atoms within the horizontal path,” Kim says. “Curiously, it has very weak Van der Waals forces, that means it doesn’t react with something vertically, which makes graphene’s floor very slippery.”

Copy and peel

The crew now stories that graphene, with its ultrathin, Teflon-like properties, might be sandwiched between a wafer and its semiconducting layer, offering a barely perceptible, nonstick floor via which the semiconducting materials’s atoms can nonetheless rearrange within the sample of the wafer’s crystals. The fabric, as soon as imprinted, can merely be peeled off from the graphene floor, permitting producers to reuse the unique wafer.

The crew discovered that its method, which they time period “distant epitaxy,” was profitable in copying and peeling off layers of semiconductors from the identical semiconductor wafers. The researchers had success in making use of their method to unique wafer and semiconducting supplies, together with indium phosphide, gallium arsenenide, and gallium phosphide — supplies which might be 50 to 100 instances costlier than silicon.

Kim says that this new method makes it potential for producers to reuse wafers — of silicon and higher-performing supplies — “conceptually, advert infinitum.”

“It is a very distinctive utility of graphene,” says Philip Kim, a pioneer within the examine of graphene, and professor of physics at Harvard College, who was not concerned within the analysis. “The method might be readily built-in into the semiconducting manufacturing course of, and should revolutionize the thin-film progress of semiconductor heterostructures … to kind novel digital and optical system purposes.”

An unique future

The group’s graphene-based peel-off method might also advance the sphere of versatile electronics. Typically, wafers are very inflexible, making the gadgets they’re fused to equally rigid. Kim says now, semiconductor gadgets comparable to LEDs and photo voltaic cells might be made to bend and twist. In reality, the group demonstrated this chance by fabricating a versatile LED show, patterned within the MIT brand, utilizing their method.

“Let’s say you wish to set up photo voltaic cells in your automobile, which isn’t utterly flat — the physique has curves,” Kim says. “Are you able to coat your semiconductor on high of it? It’s unimaginable now, as a result of it sticks to the thick wafer. Now, we will peel off, bend, and you are able to do conformal coating on vehicles, and even clothes.”

Going ahead, the researchers plan to design a reusable “mom wafer” with areas produced from completely different unique supplies. Utilizing graphene as an middleman, they hope to create multifunctional, high-performance gadgets. They’re additionally investigating mixing and matching numerous semiconductors and stacking them up as a multimaterial construction.  

“Now, unique supplies might be in style to make use of,” Kim says. “You don’t have to fret about the price of the wafer. Allow us to provide the copy machine. You’ll be able to develop your semiconductor system, peel it off, and reuse the wafer.”

This analysis was supported, partly, by the One to One Joint Analysis Venture between the MI/MIT Cooperative Program and LG electronics R&D heart.

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