Info
Info
News Article

Gallium Arsenide Etch Without The Sketch

For the first time, researchers have watched and controlled 3D gallium arsenide etching in real time
To craft some of the most complex semiconductors, manufacturers etch pre-defined patterns into wafers, carving out structures layer by layer. The processes can be time-consuming and are executed blindly, leaving few opportunities to monitor the etching or make any necessary adjustments.

Now, researchers at the University of Illinois at Urbana-Champaign have developed a technique to watch and control the etching of semiconductors as it is happening, with a height resolution on the nanometre scale.

The researchers describe the technique in the September 28th, 2012, issue of Light: Science & Applications, an open-access, peer-reviewed publication from the Nature Publishing Group.

In the paper, the researchers explain how they combined real-time observations from epi-illumination diffraction phase microscopy (epi-DPM) with photochemical etching techniques to manufacture GaAs micro-lenses as a proof-of-concept for the techniques.

"The instrumentation we are developing will allow engineers to more thoroughly understand the dynamics of their fabrication processes and make fine adjustments to the processing conditions in real-time," says principal investigator and University of Illinois at Urbana-Champaign engineering Lynford Goddard, a National Science Foundation CAREER grantee.

The technique incorporates an optical microscope, a projector, a Nd:YAG frequency doubled green laser, digital camera and a series of mirrors, lenses and filters. The setup, allowed the engineers to observe interference patterns as light bounced off of a semiconductor sample, revealing surface details as small as 2.8 nm in height.

As the camera captures interference images, software converts them to topographic height maps in real time. Each image is stable, shifting as little as 0.6 nm in height, per pixel, from frame to frame. The new process allows researchers to not only watch an etching underway, but to instantly make adjustments using a digital projector.

A National Science Foundation Major Research Instrumentation grant supported the research with matching funds from the University of Illinois.

"This optical non-invasive, non-destructive technique can monitor the dynamics of semiconductor fabrication processes in real time with nanoscale resolution," adds Leon Esterowitz, the NSF program officer who oversaw Goddard's instrumentation grant. "This 3-D technique should significantly reduce processing time, improve control of device properties, and reduce fabrication costs for a wide variety of semiconductor devices."

Currently, semiconductor manufacturers lose time and material calibrating their equipment and fabrication processes on dummy wafers before etching a retail product, and then have to do a post-etching check of the chips to ensure that the calibration during production was consistent.

The new ability to watch and control the etching in real time eliminates both the pre- and post-inspection steps. Additionally, because the technique uses optical microscopy, the semiconductor is not damaged by the illuminating source, as it would be with other electron microscope methods and techniques such as scanning electron microscopy or focused ion beam inspection.

"The exceptional stability and accuracy of our method will help to address some grand challenges in the semiconductor manufacturing industry," adds Goddard. "Besides enabling adaptive process control, we have begun to adapt the method to find isolated defects in patterned semiconductor wafers. Finding those device-killing defects can improve the overall yield during processing and reduce the cost of consumer electronics."



3-D image of the height profile of the University of Illinois logo etched in gallium-arsenide (Credit: Chris Edwards, Amir Arbabi, Gabriel Popescu, and Lynford Goddard, Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign)

The image above is a false colour 3-D image that represents the height profile of the University of Illinois logo etched onto the surface of a GaAs semiconductor substrate. The image was captured in situduring wet etching using epi-illumination diffraction phase microscopy (epi-DPM) with a laser source. A 5x objective was used and provided a 320 µm by 240 µm field of view. The total etch depth, i.e. the height difference between the orange and purple regions, was approximately 250 nm after the 45 second etch. The diagonal line in the lower left corner may be a scratch in the sample.



AngelTech Live III: Join us on 12 April 2021!

AngelTech Live III will be broadcast on 12 April 2021, 10am BST, rebroadcast on 14 April (10am CTT) and 16 April (10am PST) and will feature online versions of the market-leading physical events: CS International and PIC International PLUS a brand new Silicon Semiconductor International Track!

Thanks to the great diversity of the semiconductor industry, we are always chasing new markets and developing a range of exciting technologies.

2021 is no different. Over the last few months interest in deep-UV LEDs has rocketed, due to its capability to disinfect and sanitise areas and combat Covid-19. We shall consider a roadmap for this device, along with technologies for boosting its output.

We shall also look at microLEDs, a display with many wonderful attributes, identifying processes for handling the mass transfer of tiny emitters that hold the key to commercialisation of this technology.

We shall also discuss electrification of transportation, underpinned by wide bandgap power electronics and supported by blue lasers that are ideal for processing copper.

Additional areas we will cover include the development of GaN ICs, to improve the reach of power electronics; the great strides that have been made with gallium oxide; and a look at new materials, such as cubic GaN and AlScN.

Having attracted 1500 delegates over the last 2 online summits, the 3rd event promises to be even bigger and better – with 3 interactive sessions over 1 day and will once again prove to be a key event across the semiconductor and photonic integrated circuits calendar.

So make sure you sign up today and discover the latest cutting edge developments across the compound semiconductor and integrated photonics value chain.

REGISTER FOR FREE

VIEW SESSIONS

Info
×
Search the news archive

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

You may choose to subscribe to the Compound Semiconductor Magazine, the Compound 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:
 
X
Info
X
Info
{taasPodcastNotification}
Live Event