TRANSISTORS
©stock.adobe.com/au/Jultud
IMPROVING DEFECT DETECTION IN TRANSISTORS Researchers at the US National Institute of Standards and Technology (NIST) have revived and improved a once-reliable technique known as charging pumping to identify and count defects in transistors — the building blocks of modern electronic devices such as smartphones and computers.
T
he new and improved method is sensitive enough for the most modern, minuscule technology, and is said to provide an accurate assessment of defects that could otherwise impair the performance of transistors and limit the reliability of the chips in which they reside. It has been described in the journal Applied Physics Letters. Transistors act as electrical switches. In the on position, which represents the ‘1’ of binary digital information, a designated amount of current flows from one side of a semiconductor to the other. In the off position, representing the ‘0’ of binary logic, current ceases to flow. Defects in a transistor can interfere with the reliable flow of current and significantly degrade the performance of transistors. These defects could be broken chemical bonds in the transistor
14
MARCH/APRIL 2022
material or they could be atomic impurities that trap electrons in the material. Scientists have devised several ways to categorise defects and minimise their impact, tailored to the structure of the transistor under study. In the traditional design known as the metal oxide semiconductor field effect transistor (MOSFET), a metal electrode called the gate sits atop a thin insulating layer of silicon dioxide. Below the insulating layer lies the interface region that separates the insulating layer and the main body of the semiconductor. In a typical transistor, current travels through a narrow channel, only one billionth of a metre thick, that extends from the source, which lies on one side of the gate, to a ‘drain’ on the other side; the gate controls the amount of current in the channel. In charge pumping,
WWW.ELECTRONICSONLINE.NET.AU
