+44 (0)24 7671 8970
More publications     •     Advertise with us     •     Contact us
News Article

A tough coat for silicon

News
Super-critical carbon dioxide delivers protective molecules to semiconductor surfaces

A coating of alkylthiol molecules protects a forest of silicon nanowires. Reprinted with permission from Ref 1. Copyright 2016 American Chemical Society.

A simple, green method that applies a protective coating to semiconductors could help to develop these materials for many applications, from batteries to biosensors1.

Silicon forms an oxide layer on its surface when exposed to air or moisture, which can detract from its electronic properties. Adding a "˜skin' of molecules to the silicon can provide a physical barrier that prevents oxidation, but forming these monolayers can be tricky, requiring an inert atmosphere and long processing times, or demand the use of potentially harmful organic solvents.

Sreenivasa Reddy Puniredd of the A*STAR Institute of Materials Research and Engineering and colleagues have now developed a new way to deliver the protective molecules using supercritical carbon dioxide (scCO2). Carbon dioxide is converted to scCO2 under high pressure, when it becomes a free-flowing liquid that is chemically inert, inexpensive, and more environmentally-friendly than traditional solvents.

The researchers used scCO2 to carry molecules called alkylthiols, which contain long carbon chains with a sulfur atom at one end. Sulfur forms a stable bond with silicon, while the water-repelling carbon chains make a tightly-packed skin on silicon's surface.

To apply the coating, they used alkylthiols containing between seven and 18 carbon atoms to coat silicon, germanium, and silicon nanowires. Each procedure took a few hours, and produced monolayers between 1.6 nanometers and 2.3 nanometers thick that resisted wear and repelled water. The greatest effect was seen for the longest alkylthiol chains.

The monolayers also protected the surface from oxygen for more than 50 days; those prepared using conventional solvents were typically stable for less than seven days. "The increase in stability was expected, but such long-term stability was a surprise," says Puniredd.

Silicon nanowires are being tested for a range of biological applications, including biosensors and antibacterial surfaces. Although fragile and easily damaged by other monolayer formation methods, the silicon nanowires were undamaged by the scCO2 process, allowing the researchers to test how they interacted with human liver cells. Those protected by the 18-carbon alkylthiol significantly reduced cell growth on the nanowires, compared with unprotected nanowires or a flat silicon surface. This is probably because the cells' proteins could not latch on to the monolayer's long carbon chains.

"This scCO2 technology can be adopted for many kinds of inorganic surface modification," says Puniredd. "The technology is not only scalable, but also enhances the quality and stability of the film. It can potentially replace billions of pounds of organic solvents used every year in thin-film fabrication and cleaning applications."

The A*STAR-affiliated researchers contributing to this research are from the Institute of Materials Research and Engineering. For more information about the team's research, please visit the Materials Processing & Characterisation department webpage.


Photonis announces agreement to acquire Xenics, a leader in Infra-Red imaging solutions
Phlux Technology Secures £4m in Seed Funding
Start-ups: build up your ecosystem
Trends in the semiconductor industry
Advantest Unveils E5620 DR-SEM for Review and Classification of Ultra-Small Photomask Defects
Xenics introduces Wildcat+ 640
Advantest Introduces New inteXcell Series
Sony Semiconductor Israel Redefines IoT Connectivity Platform
Sensor Sales Stay Strong Due to Big ASP Rise
Advantest Launches ACS Solution Store to Enable Real-Time Data Analytics Solutions
Lam Research Acquires SEMSYSCO to Advance Chip Packaging
Infineon planning a major investment in a new factory in Dresden
Particle Measuring Systems introduces 10 nm aerosol particle counter
EBARA presents DYNOX Gas Abatement System
TSMC Launches OIP 3DFabric Alliance
DuPont reshapes IC materials manufacturing for post-COVID success
Evolving subfab vacuum challenges demand collaborative solutions
Next-gen low-k films can address present, future fabrication challenges
Critical Manufacturing redefines semiconductor MES for greater agility, success
Brewer Science bonding & dielectric materials deliver packaging solutions for 5G, IoT devices
Cutting FOPLP pattern distortion
EV Group advances leadership in optical lithography
ASM joins semiconductor climate consortium
KLA Launches New Double-Sided Direct Imaging Platform
Micron ships advanced DRAM technology with 1β node
Nor-Cal will do business as Pfeiffer Vacuum
ClassOne Equipment Releases Major New Lot of Used Semiconductor Tools for Resale
Park Systems Celebrates the Merger and Acquisition of Accurion GmbH
Amkor to support European semiconductor ecosystem
Nanometre components require sub-nanometre precision
ALD TechDay for More-than-Moore devices
Cadence Expands Collaboration with Samsung Foundry

{inStory3}
×
Search the news archive

To close this popup you can press escape or click the close icon.
Logo
×
Logo
×
Register - Step 1

You may choose to subscribe to the Silicon Semiconductor Magazine, the Silicon Semiconductor Newsletter, or both. You may also request additional information if required, before submitting your application.


Please subscribe me to:

 

You chose the industry type of "Other"

Please enter the industry that you work in:
Please enter the industry that you work in: