Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Double-layer capping solves two problems

17.01.2014
Using a newly developed technique, protective casings for microscale devices can be built quickly and cheaply without damaging components

Continual downsizing of technology means that researchers have to develop ever more ingenious methods of packaging and protecting their tiny devices. Jae-Wung Lee and co-workers at the A*STAR Institute of Microelectronics, Singapore, are at the forefront of efforts to develop safe but functional encasements for microelectromechanical systems (MEMS), such as sensors, switches or radio filters.


An optical image of a 400-by-400-micrometer, thin-film MEMS encapsulation developed using the new double-layer capping technique. The smaller square caps sit on top of holes, allowing access to the cavity below while protecting the devices within.

Reproduced from Ref. 1 © 2013 IOP Publishing

“MEMS devices need certain ambient conditions to operate properly and have fragile hanging structures that must be protected,” says Lee. “We developed a new thin-film encapsulation (TFE) technique to meet these two requirements.”

During TFE, a MEMS device is embedded in a ‘sacrificial layer’ of one material before adding a ‘cap layer’ of another type of material. By leaving some access channels in the cap layer, researchers can pipe in a chemical that reacts with and removes the sacrificial layer, leaving the MEMS device in a cavity protected by the cap layer.

Compared with other encasement methods, TFE can be performed cheaply using the same techniques that are used to build MEMS devices, and it produces less bulky packaging. However, previous attempts at TFE have suffered from two problems: depending on the design of the access holes in the cap layer, removing the sacrificial layer can be time consuming, and mass loading can damage moving components, such as resonators, in MEMS devices.

“Solving both these issues simultaneously is difficult because one can become severe when the other is solved,” says Lee. “We proposed fabricating the cap layer on two levels.”

The team’s design involves making a grid of square holes in the lower cap layer. A secondary square layer with four legs is deposited on top of each hole, leaving sideways access gaps underneath, rather like a chimney cap. These caps allow access for removing the sacrificial layer while protecting the device beneath from mass loading.

The researchers tested their idea using silicon oxide as the sacrificial layer and aluminum nitride for the cap layers. They were able to remove the silicon oxide using an acid vapor in just 20 minutes, compared to 8 hours for previous designs. The result was a strong, free-standing cap with a 3-micrometer-thick cavity underneath.

Lee and co-workers state that their TFE cavity design could be built using other materials and may find application beyond MEMS, for instance in microbiology. “Electrodes embedded in a TFE cavity could be used to apply electrostatic forces to biomolecules or even act as a microheater,” says Le

The A*STAR-affiliated researchers contributing to this research are from the Institute of Microelectronics.

Journal information

Lee, J.-W., Sharma, J., Singh, N. and Kwong, D.-L. Development and evaluation of a two-level functional structure for the thin film encapsulation. Journal of Micromechanics and Microengineering 23, 075013 (2013).

A*STAR Research | Research asia research news
Further information:
http://www.research.a-star.edu.sg
http://www.researchsea.com

More articles from Power and Electrical Engineering:

nachricht Siemens hands over world's largest offshore grid connection to TenneT
28.04.2015 | Siemens AG

nachricht Electromobility: Powerful Ultralight Motor for Electrically Powered Flight
28.04.2015 | Siemens AG

All articles from Power and Electrical Engineering >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Fast and Accurate 3-D Imaging Technique to Track Optically-Trapped Particles

KAIST researchers published an article on the development of a novel technique to precisely track the 3-D positions of optically-trapped particles having complicated geometry in high speed in the April 2015 issue of Optica.

Daejeon, Republic of Korea, April 23, 2015--Optical tweezers have been used as an invaluable tool for exerting micro-scale force on microscopic particles and...

Im Focus: NOAA, Tulane identify second possible specimen of 'pocket shark' ever found

Pocket sharks are among the world's rarest finds

A very small and rare species of shark is swimming its way through scientific literature. But don't worry, the chances of this inches-long vertebrate biting...

Im Focus: Drexel materials scientists putting a new spin on computing memory

Ever since computers have been small enough to be fixtures on desks and laps, their central processing has functioned something like an atomic Etch A Sketch, with electromagnetic fields pushing data bits into place to encode data.

Unfortunately, the same drawbacks and perils of the mechanical sketch board have been just as pervasive in computing: making a change often requires starting...

Im Focus: Exploding stars help to understand thunderclouds on Earth

How is lightning initiated in thunderclouds? This is difficult to answer - how do you measure electric fields inside large, dangerously charged clouds? It was discovered, more or less by coincidence, that cosmic rays provide suitable probes to measure electric fields within thunderclouds. This surprising finding is published in Physical Review Letters on April 24th. The measurements were performed with the LOFAR radio telescope located in the Netherlands.

How is lightning initiated in thunderclouds? This is difficult to answer - how do you measure electric fields inside large, dangerously charged clouds? It was...

Im Focus: On the trail of a trace gas

Max Planck researcher Buhalqem Mamtimin determines how much nitrogen oxide is released into the atmosphere from agriculturally used oases.

In order to make statements about current and future air pollution, scientists use models which simulate the Earth’s atmosphere. A lot of information such as...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

HHL Energy Conference on May 11/12, 2015: Students Discuss about Decentralized Energy

23.04.2015 | Event News

“Developing our cities, preserving our planet”: Nobel Laureates gather for the first time in Asia

23.04.2015 | Event News

HHL's Entrepreneurship Conference on FinTech

13.04.2015 | Event News

 
Latest News

Rapid Detection of Cracks and Corrosion using Magnetic Stray Flux

28.04.2015 | Innovative Products

Discovery of an unexpected function of a protein linked to neurodegenerative diseases

28.04.2015 | Life Sciences

Rubber from dandelions / Scientists identify key components in the formation of rubber

28.04.2015 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>