![]() In the first step of the test, the positive voltage attracts or pumps electrons, which are negatively charged, to the boundary or interface between the gate’s insulating layer and the body of the transistor. The gate controls the amount of current in the channel.Ĭharge pumping is a two-step process in which the examiner alternately pulses the gate with a positive test voltage, then a negative one - the alternating voltage pulses are applied at a single, set frequency. In a typical transistor, current travels through a narrow channel, only one billionth of a meter thick, that extends from the source, which lies on one side of the gate, to a “drain” on the other side. Below the insulating layer lies the interface region that separates the insulating layer and the main body of the semiconductor. 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. Scientists have devised several ways to categorize defects and limit their impact, tailored to the structure of the transistor under study. These defects could be broken chemical bonds in the transistor material or atomic impurities that trap electrons in the material. The ability to manipulate individual spins has applications in both basic research and quantum engineering and computing.ĭefects in a transistor can interfere with the reliable flow of current and significantly degrade the performance of transistors. Researchers could also use the new capability to detect and manipulate a property in each electron known as quantum spin. The new, modified charge pumping technique can detect single defects as small as the diameter of a hydrogen atom (one-tenth of a billionth of a meter) and can indicate where they’re located in the transistor. NIST’s new method is sensitive enough for the most modern technology, and can 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. Over the past decade, transistor components have become so small in high-performance computer chips that the popular method, known as charge pumping, could no longer count defects accurately.
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