Testing tamed

Engineers at Austin, Texas-based consortium,

(SEmiconductor MAnufacturing TECHnology) have developed a test device that allows semiconductor technologists to measure the important electrical characteristic of work function on a single wafer, saving time and increasing accuracy.

The device is a specially processed wafer called a terraced oxide substrate, dubbed “the wedding cake” by developers within SEMATECH's Front End Processes (FEP) Division.

It contains a stair-like pattern of oxide thicknesses - typically ranging in depth from 20 to 100 angstroms (Å) - in a series of four wide, concentric circles. A high-k/metal stack then can be deposited on the entire wafer, after which the work function can be measured on the resulting collection of oxide-and-metal stacks. Work function pertains to the ability to turn a transistor on and off, and is critical to gate functionality.

“We now have a markedly more accurate way to measure work function on a single wafer,” said Larry Larson, FEP associate director. “You can achieve a process uniformity on a single wafer that you can't across several wafers, because with one wafer, the process remains the same across the oxide layers. This represents a big breakthrough in measuring material characteristics for candidate metals.”