Silicon surfaces speed circuits

Today's computer chip makers are able to provide faster computer chips by shrinking the size of the transistors that make up a chip. The laws of physics, however, or poised to catch up with chip-makers sometime in the next decade and standard manufacturing methods will no longer be able to make smaller chip features.

Researchers from the University of Illinois at Urbana-Champaign have devised a way to use the chemistry of silicon surfaces to make smaller chip features.

The method could permit the semiconductor industry to extend the lifetime of today's basic chip manufacturing methods and so delay the need to develop completely different methods of making computer chips.

The method allows for more precise ion implantation, a process that replaces some small areas of silicon atoms with an electrically active substance, or dopant. Doped regions of the semiconductor actively conduct current. Smaller doped regions make for faster chips.

The researchers' method modifies the ability of a silicon surface to pull atoms from inside the bulk by filling some of the surface silicon bonds with nitrogen-containing gases like ammonia. The researchers have shown that is possible to draw silicon atoms knocked loose by on an implantation and leaves dopant atoms in place. These silicon atoms cause the dopant to spread out from the target area, and removing them confines the dopant to a smaller area.

The number of unused silicon bonds that can be filled with nitrogen is controlled by varying the type of nitrogen-containing gases used and the degree of exposure.

The technique promises to be easy to integrate into manufacturing production lines and could be used within a year, according to the researchers.

The researchers presented the work at the 7th International Conference on Solid-State and Integrated-Circuit Technology held in Beijing, China, October 18 to 21, 2004.