Semiconductor scanning

While silicon is still the mainstay of the industry, circuit designers also would like to put materials like gallium nitride and silicon carbide into wider use.

Such advanced semiconductor materials can operate at higher voltages and provide faster switching speeds, an important characteristic in determining how fast a semiconductor circuit can process information.

Reporting in the Applied Physics Letters, a National Institute of Standards and Technology researcher and Korean guest researcher describe a new method for scanning semiconductors for defects that may help accelerate the market for these new materials.

The duo combined an atomic force microscope with a scanning capacitance microscope and then added custom software and a simple on/off switch for the AFMs positioning laser.

The result is an instrument that can measure how fast a material generates electrical charges and then map those speeds in sections (at least for gallium nitride) that are only about 100 nm square.

Current methods for measuring switching speed (carrier lifetime) produce only bulk averages.

According to NIST co-developer Joseph Kopoanski, the system allows quick scanning of semiconductor wafers for defects that otherwise may not be found until an expensive device has already been built on the material.

Most defect in semiconductors (ie, sections with missing atoms) are presumed to slow down the speed that charges move through a material. Kopanski says further research using the new technique should determine if this assumption is correct.