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Posted: July 29, 2010

One-of-a-kind chemical formulation enables sub-50 nanometer process technology

(Nanowerk News) Nabil Mistkawi, a new Portland State University (PSU) chemistry graduate and full-time Intel employee, has invented a one-of-a-kind chemical formulation that enables sub-50 nanometer (nm) process technology for advanced microprocessors manufacturing. This novel and environmentally friendly chemical formulation saves Intel tens of millions of dollars annually.
These microprocessors serve as the "brains," or central processing units (CPUs), of today's personal computers. Microprocessors are often comprised of more than ten layers and many different materials. To successfully manufacture sub-50nm semiconductor chips, certain materials must be uniformly removed. To do this, Nabil Mistkawi implemented an elegant solution low in toxicity and high in performance.
His solution was a green chemistry concoction that would selectively dissolve certain metal, while preserving the integrity of electrical wiring components such as copper, and of insulators, that are all sandwiched together on the chip. This wet etching process is much cleaner and significantly more effective for this application than the typical chemical polishing approach to remove materials. The new process is not only effective, but also fast—completed in only two minutes.
For Intel Corporation, this "wet etching" method has served as a great, green leap forward. It was first implemented in 2006, scaled up in 2007, and has been part of the manufacturing process for current generations of Intel microprocessors. This work replaced toxic chemical formulations containing solvents that were harmful to human health as well as the environment, thus requiring strict and controlled usage protocols.
For Mistkawi, a process engineer at Intel's Hillsboro, Ore., facility, it served as the basis for his doctoral dissertation, "Fundamental Studies in Selective Wet Etching and Corrosion Processes for High Performance Semiconductor Devices," six years in the making and successfully defended this winter at Portland State University.
"I like to have students work on projects that actually amount to something tangible," says Shankar Rananavare, faculty adviser to Mistkawi and research associate professor of chemistry at PSU. "It's one thing to make it work in a test tube and beaker. It's quite another to do so at 8,000 gallons each week."
Addressing the environmental and human risks was the driving force to solve the etch selectivity challenge. This challenging task was proposed to a number of outside chemical companies and academic research labs. After one year of research they claimed that it is impossible to achieve the etch selectivity requirements. Three days after Mistkawi was asked to take a look at the problem, he had demonstrated both feasibility and proof of a concept that would prove to be cheaper, faster and cleaner.
Another fortunate byproduct of this process is actually its lack of byproduct. The chemical etching solution is 98 percent water, with fluoride content less than that of toothpaste. This "green chemistry" reduces both disposal and environmental costs. "It was nice to incorporate a green chemistry approach, but ultimately the process had to be robust enough through its performance," says Mistkawi.
The technology had been proven, but fully understanding and demonstrating the science remained important. Mistkawi continued to refine and replicate his work in labs at Intel, located in Hillsboro, Ore. At Portland State he worked to understand the science behind the process, meeting weekly with his adviser and other doctoral students (who agreed to meet on Friday evenings to accommodate Mistkawi's work schedule). Mistkawi also worked closely with the U.S. Department of Energy's National Energy Technology Laboratory in Albany, Ore., ( to better understand corrosion science of metal thin films.
"As good as the technology was, we wanted to make sure the science behind the process was equally well understood," says PSU's Rananavare.
Nabil Mistkawi received his doctorate at Portland State University commencement ceremonies in June 2010—one of the first ten students to complete this relatively new program. He continues to work full-time for Intel, where he is an inventor on nine patent applications filed since 2003, and is considering joining the component research team, focused on path-finding research challenges. He has received numerous awards, including the 2006 Global Intel Gold Award, given annually to an Intel employee who is engaged in a project that demonstrates exceptional environmental leadership.
Mistkawi earned a double major in biochemistry and chemistry at University of Oregon. He lives with his wife and three children in Keizer, Ore.
Portland State University has long-standing connections with regional industry—PSU already provides more graduates to Intel Oregon than any other university. These connections, with an emphasis on addressing industry challenges, benefit business, while helping expand and refine curriculum. Mistkawi's work in wet etching has already contributed to future coursework for other graduate science and engineering students at PSU.
"This story is a great example of how faculty at Portland State University partner at both an educational and research level with local industry" say Kevin Reynolds, professor and chair of PSU's Department of Chemistry. "It is one of the great strengths of our institution and as this example shows, the results can have a global impact with both positive economic and environmental outcomes."
Source: Portland State University
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