Graduate Profile

Euan Ramsay, MSci Physics with Photonics 2001

Optical Engineer, San Francisco

Euan with his photonics research kit

 

After graduating with my MPhys in Physics with Photonics in 2001 I joined the research group of Dr. (now Prof.) Derryck Reid at Heriot-Watt University in Edinburgh, looking into optical methods for extracting information from silicon integrated circuits – which is what I still am doing today. After a couple of side projects in the fields of laser material processing and metrology, plus working as a postdoctoral researcher for Derryck, I left Scotland for pastures new and moved to Boston, Massachusetts, to work with Profs Bennett Goldberg and Selim Unlu in the Photonics Center at Boston University. Here I worked on new lens designs for silicon imaging, and stayed there for two years (including one winter where we had over two metres of snow!)

I am now working as a research scientist for a company called DCG Systems in the San Francisco Bay Area (no snow…) which builds microscopes for the semiconductor industry to determine the location of faults in computer chips.

Silicon is what makes the world go round these days – technology is everywhere and reliant on silicon chips to make them work. The semiconductor fabrication industry is around a $400 billion per year industry. Although each individual chip is relatively inexpensive, companies make billions of chips annually to recover their costs. If a chip design does not work the way it should, this can cost millions in lost revenues as companies try to determine why the chip failed. Sometimes it is obvious; a process step missed, for example. Other times the defect may not be obvious – it may be that the chip works fine at low power but doesn’t work at full power, or that the chip is a little slower than it should be if the voltage is off by a few millivolts. In these cases it can take a long time to diagnose the problem.

That is where companies like the one I work for come in; instead of relying on the chip executing a program to determine where the fault is, our tools can literally watch the chip running in real time. A switching transistor emits light (never let anyone tell you silicon does not emit!) and we can see that light through the back of the chip.

A very bright transistor is usually an indication that the transistor switch is leaking, which is very bad for battery life in your mobile device. Or, a transistor in the off-state has a slightly different refractive index to one in the on-state, so the reflected light from a laser will change intensity as the transistor switches – we can detect that, even at multi-GHz rates, and watch for regions where the transistor does not clock as expected. We even have more complex methods of probing where we use the light to change the timing in the circuit and look for weak points in the chip design.

In essence, our optical tools are the equivalent of medical diagnostics like CT or MRI, but using light and in silicon chips, not people. The challenge is to localise the signals to a single transistor – so my challenge is to make better optical systems to focus the light to smaller spots.

 

First posted BDS 11.15