Big lasers, tiny circuits
Slava Rokitski describes how a childhood interest in the way things work led him to a career in laser manufacturing
When it comes to computers, small is big. The more we are able to shrink the patterns of circuitry on semiconductor wafers, the smaller and more powerful the chips made from these wafers become. This in turn leads to smaller and more powerful electronic de_vices – not just computers, but also phones, global positioning systems and medical equipment. Many of the people involved in this process come from a computing or materials-science background, but there are also roles for physicists like me, who help develop and build the lasers that make it possible to create ever smaller circuits.
I work for Cymer, a company based in San Diego, California, that specializes in excimer lasers. This type of laser uses light emitted via energy transitions of excited dimers – two-particle bound states created by electrical discharge in a specially prepared mix of inert gases and fluorine. Excimer lasers have several applications, including eye surgery, but the models that Cymer makes are used by semiconductor manufacturers to create patterns on semiconductor wafers, thus enabling the creation of the computer chips used to power the world's electronic devices. From the iPhone to your new flat-screen television, Cymer's lasers probably helped create the chip inside.
Manufacturing with light
When I was growing up in Ukraine, my heart and mind always turned to science. Like many other curious kids, I liked to take things apart to see what was inside, but my first encounter with physics came at the age of seven, when I read a book called Physics for Children. It explained in great detail how one could perform simple experiments at home, and I liked to verify for myself how it all worked in practice. When I was 11, I joined a specialized physics class, and the thought of one day becoming a physicist, scientist or engineer kept me going through even the toughest educational curricula. I earned a diploma in physics from Moscow State University in 1997, followed by a Master's degree in electrical engineering (specializing in photonics) from the University of California, San Diego (UCSD) in 2001. I then stayed on at UCSD to earn my PhD in the same subject.
During the last year of my PhD, I studied the propagation of light along metal surfaces. This work brought me into contact with Cymer, which had been founded in 1986 by two UCSD PhD students, Robert Akins and Richard Sandstrom. After years of developing deep-ultraviolet excimer lasers for the US government, they had realized that there was a commercial application for excimer-laser technology in the burgeoning semiconductor and electronic manufacturing market.
Although it was only a small project, I really enjoyed the time I spent working with Cymer as a PhD student. Previously, I had never dealt with excimer lasers, so it was interesting for me to explore this unknown territory and to understand how these complex devices work. So after I finished my PhD, I joined the company permanently.
Today, I work at Cymer's San Diego headquarters as a staff systems engineer. My daily role is to lead the technical aspects of development and support for two of the company's product lines, known as XLA and XLR. In particular, I am the lead scientist working on the XLR 600ix, one of our most advanced light sources. These products can create chip features as small as 32 nm – below the diffraction limit. In addition to co-ordinating the technical design and overall performance of the system, I am also involved in the manufacturing production process itself, and with ensuring successful installations of our light sources at chip_makers around the world.
As well as overseeing these two products at the systems level, my work also involves identifying current issues with the firm's existing technology, and understanding the gaps that stand in the way of necessary advances. Semiconductor-photolithography processes depend critically on the quality of light being used for wafer exposure, since this affects the quality of the image projected onto the wafers. This means that tight control of all the laser's optical parameters – particularly the energy, wavelength and bandwidth stability of light at the semiconductor wafer – is essential in modern chip-manufacturing processes.
Advice and reflections
This month marks my fifth anniversary at Cymer, and though I am still considered relatively young in my industry, I have often been asked what advice I have for those pursuing a similar career. In general, I would say that it is important to develop a good portfolio of skills, including both technical expertise and the ability to organize and lead projects to completion. You need a passion for continuous learning in technical and non-technical fields, and, moreover, you should be interested in sharing new findings with your peers and with the technical community at large.
One of the biggest benefits of my job is that I am always learning new things as a result of continual and ongoing changes in the semiconductor industry that force me to keep pace with many different technology areas, and to apply that knowledge to continuously improve Cymer's lasers. I also find it exciting to apply the skills I had developed during graduate school to light sources at the cutting edge of technology in laser physics, optics, materials science and control systems. Skills such as troubleshooting complex systems, practical experience in the optics lab and advanced data analysis are all essential for someone with responsibility for a particular product. And because the performance of a laser system is determined by the hardware configuration and software control, anyone wishing to succeed in this area will find that solid backgrounds in physics, optics, signal processing and computer programming are all highly beneficial.
The continuous reduction of the feature size of semiconductor chips – and the technological barriers this represents – creates a fruitful environment for applying new technologies. Anyone who is motivated by the possibility of finding innovative solutions to these challenging issues will have a plethora of opportunities to choose from. So do I love my job? Absolutely – it is a wonderful feeling to know my work contributes to the betterment of humankind. And, it is a lot of fun!
About the author
Slava Rokitski is a staff systems engineer at Cymer. (email@example.com)
This article originally appeared in the June 2010 issue of Physics World.
last edited: May 11, 2015