NIST Seeks Better Chips

Highly ionized plasmas, which occur naturally only in deep space, have become a hot topic in microelectronics. Plasmas are gaseous forms of atoms that are missing one or more of their electrons. Because of their recent basic research in this area, National Institute of Standards and Technology (NIST) physicists have been invited to help turn this form of matter into a practical tool.

With support from International SEMATECH, NIST researchers are using a facility known as an electron beam ion trap (EBIT) to study questions related to the use of plasma light sources in extreme ultraviolet lithography. This type of lithography can make features much smaller than those in today’s commercial integrated circuits. But a better understanding of the plasma’s behavior is needed to make the plasma light source approach cost effective.

Inside the EBIT, high-velocity collisions separate electrons from atoms, and the resulting ions with large positive charges are confined in a vacuum chamber by magnetic and electric fields. The EBIT produces and traps ions stripped of as many as 70 electrons or as few as one, with a high degree of selectivity.

A number of issues must be addressed before plasma lithography can become a practical technology. For instance, light source efficiency must be improved more than tenfold, so NIST researchers are trying to determine whether this can be done with the xenon plasma sources already in development or whether a new strategy is needed. In this work, NIST measurements will be used to test and improve mathematical plasma models being developed elsewhere. The NIST EBIT also is being used to study the problem of highly charged ions damaging the mirrors used to focus the plasma light.

For details contact John Gillaspy, phone: (301) 975-3236, email: john.gillaspy@nist.gov.