A flexible, low-cost technique could lead to the mass production of microelectromechanical systems

March 16, 2018, Agency for Science, Technology and Research (A*STAR), Singapore
A flexible, low-cost technique could lead to the mass production of microelectromechanical systems
Tapered contact opening fabricated by new two-step plasma etching process. Credit: IEEE

Making increasingly smaller microelectromechanical systems (MEMS) has proved very challenging, limiting their anticipated potential. Now, researchers at A*STAR have developed a versatile and cost-effective technique for making devices with much greater precision and reliability for use in biotechnology and medical applications.

MEMS are used in applications ranging from airbag systems and display screens, to inkjet cartridges. They are tiny devices that combine mechanical and electrical components. Current manufacturing technologies, however, are expensive and lack the precision for making devices with micron and sub-micron scale features.

This led Vladimir Bliznetsov and colleagues from the A*STAR Institute of Microelectronics to develop a versatile and low-cost method for fabricating MEMS at dimensions not previously possible, edging closer to the mass production of smaller and more reliable devices for a range of new applications.

"MEMS are following the general trend of miniaturization in electronics, with devices that are reducing in size from the tens of microns to one micron or less," says Bliznetsov. "But the techniques used to manufacture top metal contacts to devices with such microscopic dimensions are costly and unreliable."

Current methods for creating channels, called vias, with tapered sidewalls in MEMS at scales of five microns or less, are not dependable. The method, with sidewall polymerization, is not suitable as the width at the bottom of the vias shrink considerably. Another method, involving the transfer of a profile into an etched layer, limits the maximal depth of vias due to excessive loss of the photoresist mask resulting in unacceptably rough sidewalls.

To overcome these restrictions, the researchers developed a two-step plasma etching process. This combines firstly photoresist tapering, which modifies the photoresist from a vertical to a tapered profile, and then an oxide etching with sidewall polymerization with better selectivity to photoresist. This produces vias with minimal dimensions down to 1.5 microns, and smooth sidewalls with angles of around 70 degrees.

"We combined two effects which are usually harmful during the etching process—accelerated corner sputtering and sidewall polymerization," explains Bliznetsov.

Combining these processes into a two-step achieves greater control over the etching process and produces micron-sized vias with smooth, tapered walls. And by minimizing the sidewall angle of the vias, it is possible to fabricate devices that can be better protected and have more reliable metal contacts, greatly improving their performance.

"Precise control of sidewall angle has use in many applications, and we are now planning to fabricate functional magnetic memory cells, which require pillars of magnetic material with sidewalls having a specific angle," says Bliznetsov.

Explore further: Low-cost technique for etching nanoholes in silicon could underpin new filtration and nanophotonic devices

More information: Vladimir Bliznetsov et al. MEMS Industry-Worth Etching to Fabricate Tapered Structures in SiO2, Journal of Microelectromechanical Systems (2017). DOI: 10.1109/JMEMS.2017.2755046

Related Stories

A marriage of light-manipulation technologies

February 28, 2018

Researchers have, for the first time, integrated two technologies widely used in applications such as optical communications, bio-imaging and Light Detection and Ranging (LIDAR) systems that scan the surroundings of self-driving ...

MEMS chips get metatlenses

February 20, 2018

Lens technologies have advanced across all scales, from digital cameras and high bandwidth in fiber optics to the LIGO lab instruments. Now, a new lens technology that could be produced using standard computer-chip technology ...

NIST polishes method for creating tiny diamond machines

September 28, 2011

(PhysOrg.com) -- Diamonds may be best known as a symbol of long-lasting love. But semiconductor makers are also hoping they'll pan out as key components of long-lasting micromachines if a new method developed at the National ...

Plasma etching pushes the limits of a shrinking world

November 10, 2011

Plasma etching (using an ionized gas to carve tiny components on silicon wafers) has long enabled the perpetuation of Moore's Law -- the observation that the number of transistors that can be squeezed into an integrated circuit ...

Recommended for you

Team breaks world record for fast, accurate AI training

November 7, 2018

Researchers at Hong Kong Baptist University (HKBU) have partnered with a team from Tencent Machine Learning to create a new technique for training artificial intelligence (AI) machines faster than ever before while maintaining ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.