{"id":12083,"date":"2017-04-20T07:51:56","date_gmt":"2017-04-20T07:51:56","guid":{"rendered":"http:\/\/revoscience.com\/en\/?p=12083"},"modified":"2017-04-20T07:51:56","modified_gmt":"2017-04-20T07:51:56","slug":"not-stuck-silicon","status":"publish","type":"post","link":"https:\/\/www.revoscience.com\/en\/not-stuck-silicon\/","title":{"rendered":"Not stuck on silicon"},"content":{"rendered":"

Engineers use graphene as a \u201ccopy machine\u201d to produce cheaper semiconductor wafers.\u00a0<\/strong><\/em><\/span><\/p>\n

\"\"
(Left to right): Postdoc Kyusang Lee, Professor Jeehwan Kim (sitting), and graduate students Samuel Cruz and Yunjo Kim.
Photo: Jose-Luis Olivares\/MIT<\/figcaption><\/figure>\n

CAMBRIDGE, Mass. —\u00a0In 2016, annual global semiconductor sales reached their highest-ever point, at $339 billion worldwide. In that same year, the semiconductor industry spent about $7.2 billion worldwide on wafers that serve as the substrates for microelectronics components, which can be turned into transistors, light-emitting diodes, and other electronic and photonic devices.<\/span><\/p>\n

A new technique developed by MIT engineers may vastly reduce the overall cost of wafer technology and enable devices made from more exotic, higher-performing semiconductor materials than conventional silicon.<\/span><\/p>\n

The new method, reported today in Nature<\/em>, uses graphene \u2014 single-atom-thin sheets of graphite \u2014 as a sort of \u201ccopy machine\u201d to transfer intricate crystalline patterns from an underlying semiconductor wafer to a top layer of identical material.<\/span><\/p>\n

The engineers worked out carefully controlled procedures to place single sheets of graphene onto an expensive wafer. They then grew semiconducting material over the graphene layer. They found that graphene is thin enough to appear electrically invisible, allowing the top layer to see through the graphene to the underlying crystalline wafer, imprinting its patterns without being influenced by the graphene.<\/span><\/p>\n

Graphene is also rather \u201cslippery\u201d and does not tend to stick to other materials easily, enabling the engineers to simply peel the top semiconducting layer from the wafer after its structures have been imprinted.<\/span><\/p>\n

Jeehwan Kim, the Class of 1947 Career Development Assistant Professor in the departments of Mechanical Engineering and Materials Science and Engineering, says that in conventional semiconductor manufacturing, the wafer, once its crystalline pattern is transferred, is so strongly bonded to the semiconductor that it is almost impossible to separate without damaging both layers.<\/span><\/p>\n

\u201cYou end up having to sacrifice the wafer \u2014 it becomes part of the device,\u201d Kim says. \u00a0<\/span><\/p>\n

With the group\u2019s new technique, Kim says manufacturers can now use graphene as an intemediate layer, allowing them to copy and paste the wafer, separate a copied film from the wafer, and reuse the wafer many times over. In addition to saving on the cost of wafers, Kim says this opens opportunities for exploring more exotic semiconductor materials.<\/span><\/p>\n

\u201cThe industry has been stuck on silicon, and even though we\u2019ve known about better performing semiconductors, we haven\u2019t been able to use them, because of their cost,\u201d Kim says. \u201cThis gives the industry freedom in choosing semiconductor materials by performance and not cost.\u201d<\/span><\/p>\n

Kim\u2019s research team discovered this new technique at MIT\u2019s Research Laboratory of Electronics. Kim\u2019s MIT co-authors are first author and graduate student Yunjo Kim; graduate students Samuel Cruz, Babatunde Alawonde, Chris Heidelberger, Yi Song, and Kuan Qiao; postdocs Kyusang Lee, Shinhyun Choi, and Wei Kong; visiting research scholar Chanyeol Choi; Merton C. Flemings-SMA Professor of Materials Science and Engineering Eugene Fitzgerald; professor of electrical engineering and computer science Jing Kong; and assistant professor of mechanical engineering Alexie Kolpak; along with Jared Johnson and Jinwoo Hwang from Ohio State University, and Ibraheem Almansouri of Masdar Institute of Science and Technology.<\/span><\/p>\n

Graphene shift<\/strong><\/span><\/p>\n

Since graphene\u2019s discovery in 2004, researchers have been investigating its exceptional electrical properties in hopes of improving the performance and cost of electronic devices. Graphene is an extremely good conductor of electricity, as electrons flow through graphene with virtually no friction. Researchers, therefore, have been intent on finding ways to adapt graphene as a cheap, high-performance semiconducting material.<\/span><\/p>\n

\u201cPeople were so hopeful that we might make really fast electronic devices from graphene,\u201d Kim says. \u201cBut it turns out it\u2019s really hard to make a good graphene transistor.\u201d<\/span><\/p>\n

In order for a transistor to work, it must be able to turn a flow of electrons on and off, to generate a pattern of ones and zeros, instructing a device on how to carry out a set of computations. As it happens, it is very hard to stop the flow of electrons through graphene, making it an excellent conductor but a poor semiconductor.<\/span><\/p>\n

Kim\u2019s group took an entirely new approach to using graphene in semiconductors. Instead of focusing on graphene\u2019s electrical properties, the researchers looked at the material\u2019s mechanical features.<\/span><\/p>\n

\u201cWe\u2019ve had a strong belief in graphene, because it is a very robust, ultrathin, material and forms very strong covalent bonding between its atoms in the horizontal direction,\u201d Kim says. \u201cInterestingly, it has very weak Van der Waals forces, meaning it doesn\u2019t react with anything vertically, which makes graphene\u2019s surface very slippery.\u201d<\/span><\/p>\n

Copy and peel<\/strong><\/span><\/p>\n

The team now reports that graphene, with its ultrathin, Teflon-like properties, can be sandwiched between a wafer and its semiconducting layer, providing a barely perceptible, nonstick surface through which the semiconducting material\u2019s atoms can still rearrange in the pattern of the wafer\u2019s crystals. The material, once imprinted, can simply be peeled off from the graphene surface, allowing manufacturers to reuse the original wafer.<\/span><\/p>\n

The team found that its technique, which they term \u201cremote epitaxy,\u201d was successful in copying and peeling off layers of semiconductors from the same semiconductor wafers. The researchers had success in applying their technique to exotic wafer and semiconducting materials, including indium phosphide, gallium arsenenide, and gallium phosphide \u2014 materials that are 50 to 100 times more expensive than silicon.<\/span><\/p>\n

Kim says that this new technique makes it possible for manufacturers to reuse wafers \u2014 of silicon and higher-performing materials \u2014 \u201cconceptually, ad infinitum.\u201d<\/span><\/p>\n

An exotic future<\/strong><\/span><\/p>\n

The group\u2019s graphene-based peel-off technique may also advance the field of flexible electronics. In general, wafers are very rigid, making the devices they are fused to similarly inflexible. Kim says now, semiconductor devices such as LEDs and solar cells can be made to bend and twist. In fact, the group demonstrated this possibility by fabricating a flexible LED display, patterned in the MIT logo, using their technique.<\/span><\/p>\n

\u201cLet\u2019s say you want to install solar cells on your car, which is not completely flat \u2014 the body has curves,\u201d Kim says. \u201cCan you coat your semiconductor on top of it? It\u2019s impossible now, because it sticks to the thick wafer. Now, we can peel off, bend, and you can do conformal coating on cars, and even clothing.\u201d<\/span><\/p>\n

Going forward, the researchers plan to design a reusable \u201cmother wafer\u201d with regions made from different exotic materials. Using graphene as an intermediary, they hope to create multifunctional, high-performance devices. They are also investigating mixing and matching various semiconductors and stacking them up as a multimaterial structure. \u00a0<\/span><\/p>\n

\u201cNow, exotic materials can be popular to use,\u201d Kim says. \u201cYou don\u2019t have to worry about the cost of the wafer. Let us give you the copy machine. You can grow your semiconductor device, peel it off, and reuse the wafer.\u201d<\/span><\/p>\n

This research was supported, in part, by the One to One Joint Research Project between the MI\/MIT Cooperative Program and LG electronics R&D center.<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

Engineers use graphene as a \u201ccopy machine\u201d to produce cheaper semiconductor wafers.\u00a0 CAMBRIDGE, Mass. —\u00a0In 2016, annual global semiconductor sales reached their highest-ever point, at $339 billion worldwide. In that same year, the semiconductor industry spent about $7.2 billion worldwide on wafers that serve as the substrates for microelectronics components, which can be turned into […]<\/p>\n","protected":false},"author":6,"featured_media":12084,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[34,28],"tags":[],"class_list":["post-12083","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-economics","category-techbiz"],"featured_image_urls":{"full":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/04\/MIT-Graphene-CopyPaste-1_0.jpg",511,341,false],"thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/04\/MIT-Graphene-CopyPaste-1_0-150x150.jpg",150,150,true],"medium":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/04\/MIT-Graphene-CopyPaste-1_0-300x200.jpg",300,200,true],"medium_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/04\/MIT-Graphene-CopyPaste-1_0.jpg",511,341,false],"large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/04\/MIT-Graphene-CopyPaste-1_0.jpg",511,341,false],"1536x1536":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/04\/MIT-Graphene-CopyPaste-1_0.jpg",511,341,false],"2048x2048":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/04\/MIT-Graphene-CopyPaste-1_0.jpg",511,341,false],"ultp_layout_landscape_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/04\/MIT-Graphene-CopyPaste-1_0.jpg",511,341,false],"ultp_layout_landscape":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/04\/MIT-Graphene-CopyPaste-1_0.jpg",511,341,false],"ultp_layout_portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/04\/MIT-Graphene-CopyPaste-1_0.jpg",511,341,false],"ultp_layout_square":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/04\/MIT-Graphene-CopyPaste-1_0.jpg",511,341,false],"newspaper-x-single-post":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/04\/MIT-Graphene-CopyPaste-1_0.jpg",511,341,false],"newspaper-x-recent-post-big":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/04\/MIT-Graphene-CopyPaste-1_0.jpg",511,341,false],"newspaper-x-recent-post-list-image":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/04\/MIT-Graphene-CopyPaste-1_0.jpg",95,63,false],"web-stories-poster-portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/04\/MIT-Graphene-CopyPaste-1_0.jpg",511,341,false],"web-stories-publisher-logo":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/04\/MIT-Graphene-CopyPaste-1_0.jpg",96,64,false],"web-stories-thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/04\/MIT-Graphene-CopyPaste-1_0.jpg",150,100,false]},"author_info":{"info":["Amrita Tuladhar"]},"category_info":"Economics<\/a> Tech<\/a>","tag_info":"Tech","comment_count":"0","_links":{"self":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/12083","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/comments?post=12083"}],"version-history":[{"count":0,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/12083\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media\/12084"}],"wp:attachment":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media?parent=12083"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/categories?post=12083"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/tags?post=12083"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}