Smaller features, faster wafers

As Moore’s law – the doubling every two years of the number of transistors on an integrated circuit – moves closer and closer, the semiconductor industry is looking for ways to make microchips faster and faster. And a new 13.5-nm extreme-ultraviolet (EUV) light source could reduce feature size on chips by approximately one order of magnitude, speeding them up significantly.

False-color images of the tin and lithium plasma plumes in EUV emission through a 7- to 15-nm filter, obtained under identical conditions. Courtesy of the American Institute of Physics.

To generate light at the 13.5-nm wavelength, tin (Sn) or lithium (Li) targets can be bombarded with laser beams, creating an intensely bright plasma. Purdue University graduate student Ryan Coons and 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 their group modeled their physical processes.

The researchers compared the atomic and ionic debris and examined the emission features of Sn and Li plasmas to find that the Sn variety produced twice as much emission as Li plasmas. The kinetic energy of Sn ions is far higher, but with a lower flux. The researchers are working to perfect the development of this technology.

The work was published in the Journal of Applied Physics, Vol. 108, p. 063306 (2010).