Science Update: Fundamental photoresist chemistry findings could help extend Moore's Law

When low concentrations of crosslinker are added to the resist (left), it is able to pattern smaller features and doesn't require longer, expensive exposures as with a high concentrations of crosslinker (right). Credit: Prashant Kulshreshtha, Berkeley Lab

( —Over the years, computer chips have gotten smaller thanks to advances in materials science and manufacturing technologies. This march of progress, the doubling of transistors on a microprocessor roughly every two years, is called Moore's Law. But there's one component of the chip-making process in need of an overhaul if Moore's law is to continue: the chemical mixture called photoresist. Similar to film used in photography, photoresist, also just called resist, is used to lay down the patterns of ever-shrinking lines and features on a chip.

Now, in a bid to continue decreasing transistor size while increasing computation and energy efficiency, chip-maker Intel has partnered with researchers from the U.S. Department of Energy's Lawrence Berkeley National Lab (Berkeley Lab) to design an entirely new kind of resist. And importantly, they have done so by characterizing the chemistry of photoresist, crucial to further improve performance in a systematic way. The researchers believe their results could be easily incorporated by companies that make resist, and find their way into manufacturing lines as early as 2017.

The new resist effectively combines the material properties of two pre-existing kinds of resist, achieving the characteristics needed to make smaller features for microprocessors, which include better light sensitivity and mechanical stability, says Paul Ashby, staff scientist at Berkeley Lab's Molecular Foundry, a DOE Office of Science user facility. "We discovered that mixing chemical groups, including cross linkers and a particular type of ester, could improve the resist's performance." The work is published this week in the journal Nanotechnology.

Finding a new kind of photoresist is "one of the largest challenges facing the semiconductor industry in the materials space," says Patrick Naulleau, director of the Center for X-ray Optics (CXRO) at Berkeley Lab.

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