Smaller Features, Faster Wafers

The manufacturing of semiconductor wafers used in all types of electronics involves etching small features onto a wafer with lasers. This process ultimately is limited by the wavelength of the light itself. The semiconductor industry is rapidly approaching this fundamental limit for increasing the speed of the microchip. The development of a new, intense 13.5-nm (extreme-UV) light source will resolve this issue by reducing the feature size by an order of magnitude or so, according to a study in the Journal of Applied Physics carried out by Purdue researchers.

One way to generate this wavelength of light is to bombard tin and lithium targets with laser beams to create an intensely bright plasma. Tin and lithium are good candidates because their plasmas emit efficiently in the 13.5-nm region, says graduate student Ryan Coons. He and his colleagues used spectroscopy and a Faraday cup to analyze the emission features and debris produced in laser-produced tin and lithium plasmas, and others in his group modeled their physical processes.

False-color images of tin and lithium plasma plumes in extreme-UV emission through a 7- to 15-nm filter, obtained under identical conditions. (Image: American Institute of Physics)

In a detailed comparison of the atomic and ionic debris, as well as the emission features of tin and lithium plasmas, the group showed that tin plasmas produce twice as much emission as lithium plasmas. However, the kinetic energy of tin ions is considerably higher, though with a lower flux. More work is needed to perfect the development of this technology.

The article, “Analysis of atomic and ion debris features of laser-produced Sn and Li plasmas,” was authored by Ryan W. Coons, Sivanandan S. Harilal, David D. Campos and Ahmed Hassanein.

For more information, visit: jap.aip.org