Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Etching of deep trenches in silicon explained

05.02.2004


Dutch researcher Michiel Blauw has described the physical limitations of the plasma-etching of deep, narrow microstructures in silicon. His results have led to such an improvement in the etching process that trenches with a depth more than 30 times their width can now be made. This is important for the production of sensitive sensors.



Blauw investigated fluorine-based plasma etching processes. A plasma with a high ion-density ’burns’ a small hole in silicon. Many applications require narrow, deep holes. Blauw studied how the plasma reacts with the silicon and how the sidewalls must be treated so as to make the trench as deep and as straight as possible.

The researcher came up with two ways to improve the profile of the trenches in the so-called Bosch process. During this process, a polymer layer ensures that the sidewalls are not etched by the plasma. However, the thin polymer layer is also deposited onto the bottom of the trench and this hinders the etching of deep, narrow trenches.


Firstly the researcher added a third plasma pulse to the Bosch-process after the etching and passivation pulses. This efficiently removed the polymer layer from the bottom of the trench. A patent has been granted for this method. Secondly he optimised the passivation pulse used to treat the sidewalls so that no polymer deposition occurred on the bottom of the trenches.
This made a maximum depth-width ratio of more than 30 possible.

In principle, the etching of silicon occurs at the same speed in all directions. To obtain the deep, narrow trenches necessary for accurate sensors, the sidewalls must be made insensitive to the plasma. This is termed passivating. After a variety of experiments in which he added oxygen to the plasma or deposited a polymer layer, Blauw found an effective passivating technique. A plasma with a high ion-density removes the passivating layer from the surface. This results in deep, narrow trenches because the ions are accelerated perpendicular to the substrate. He also found that the etch rate as a function of the depth-width ratio can be controlled by tuning the ion-density.

Plasma-etching provides considerable advantages for the manufacture of inertial sensors such as accelerometers and gyroscopes. This is because the manufacturing processes for the sensor and the electronics for signal processing are compatible, allowing both parts to be integrated onto a single chip. Furthermore, increasing the depth-width ratio of the etched microstructures considerably improves the integration density and accuracy of these devices.

The research was funded by the Technology Foundation STW.

Sonja Jacobs | NWO
Further information:
http://www.nwo.nl

More articles from Materials Sciences:

nachricht Osaka university researchers make the slipperiest surfaces adhesive
18.10.2017 | Osaka University

nachricht Think laterally to sidestep production problems
17.10.2017 | King Abdullah University of Science & Technology (KAUST)

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Osaka university researchers make the slipperiest surfaces adhesive

18.10.2017 | Materials Sciences

Space radiation won't stop NASA's human exploration

18.10.2017 | Physics and Astronomy

Los Alamos researchers and supercomputers help interpret the latest LIGO findings

18.10.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>