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 Trojan Transit Rolling Out
27.03.2015 | University of Arkansas at Little Rock

nachricht Ultra-Thin Silicon Films Create Vibrant Optical Colors
25.03.2015 | University of Alabama Huntsville

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: Experiment Provides the Best Look Yet at 'Warm Dense Matter' at Cores of Giant Planets

In an experiment at the Department of Energy's SLAC National Accelerator Laboratory, scientists precisely measured the temperature and structure of aluminum as...

Im Focus: Energy-autonomous and wireless monitoring protects marine gearboxes

The IPH presents a solution at HANNOVER MESSE 2015 to make ship traffic more reliable while decreasing the maintenance costs at the same time. In cooperation with project partners, the research institute from Hannover, Germany, has developed a sensor system which continuously monitors the condition of the marine gearbox, thus preventing breakdowns. Special feature: the monitoring system works wirelessly and energy-autonomously. The required electrical power is generated where it is needed – directly at the sensor.

As well as cars need to be certified regularly (in Germany by the TÜV – Technical Inspection Association), ships need to be inspected – if the powertrain stops...

Im Focus: 3-D satellite, GPS earthquake maps isolate impacts in real time

Method produced by UI researcher could improve reaction time to deadly, expensive quakes

When an earthquake hits, the faster first responders can get to an impacted area, the more likely infrastructure--and lives--can be saved.

Im Focus: Atlantic Ocean overturning found to slow down already today

The Atlantic overturning is one of Earth’s most important heat transport systems, pumping warm water northwards and cold water southwards. Also known as the Gulf Stream system, it is responsible for the mild climate in northwestern Europe. 

Scientists now found evidence for a slowdown of the overturning – multiple lines of observation suggest that in recent decades, the current system has been...

Im Focus: Robot inspects concrete garage floors and bridge roadways for damage

Because they are regularly subjected to heavy vehicle traffic, emissions, moisture and salt, above- and underground parking garages, as well as bridges, frequently experience large areas of corrosion. Most inspection systems to date have only been capable of inspecting smaller surface areas.

From April 13 to April 17 at the Hannover Messe (hall 2, exhibit booth C16), engineers from the Fraunhofer Institute for Nondestructive Testing IZFP will be...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

World Conference On Regenerative Medicine 2015: Registration And Abstract Submission Now Open

25.03.2015 | Event News

University presidents from all over the world meet in Hamburg

19.03.2015 | Event News

10. CeBiTec Symposium zum Big Data-Problem

17.03.2015 | Event News

 
Latest News

Researchers discover how body's good fat tissue communicates with brain

30.03.2015 | Life Sciences

For drivers with telescopic lenses, driving experience and training affect road test results

30.03.2015 | Health and Medicine

Climate change does not cause extreme winters

30.03.2015 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>