The charge-based corona-Kelvin non-contact metrology, originally developed for Si IC fabrication, has recently been extended to wide energy gap semiconductors. We discuss principles of this extension and key applications, namely: high precision dopant measurement on SiC and GaN; two-dimensional electron gas characterization in AlGaN/GaN HEMT structures; interface and dielectric characterization on epi-layers with SiO 2 and SiN; comprehensive interfacial instability characterization of oxidized SiC; and whole wafer mapping of defects with a charge-assisted surface voltage technique, QUAD. This powerful set of measurements is performed without fabrication of any test structures or electrical contact. Corresponding commercial tools are currently being introduced. Based on the historical example of silicon IC, we believe that this approach shall offer enhanced testing for research and for manufacturing process control with reduced cost and fast data feedback benefiting wide-bandgap device technology.
. This paper is part of the JSS Focus Issue on GaN-Based Electronics for Power, RF, and Rad-Hard Applications.Development of semiconductor devices and control of the manufacturing process requires cost effective metrology with rapid feedback to pilot or manufacturing lines. In this respect, silicon IC's have been benefiting from inventions (by IBM, Fishkill, NY 1 and by SDI, Tampa, FL 2 ) that created a foundation for the unique charge-based non-contact electrical metrology.
3In this technique, an electrical biasing is produced by corona charging of a surface and the response is monitored by measuring the surface voltage with a vibrating probe, such as a Kelvin-probe. The technique is commonly referred to as the corona-Kelvin method. 4 Corresponding commercial tools designed for Si wafers reduced the need for fabrication of electrical test devices and electric contacts; lowering the manufacturing cost and shortening the data feedback time from weeks to less than one hour. 5 The metrology has been continuously improved in sensitivity, precision, repeatability, and spatial resolution; meeting the demands of new technology nodes. It has been used by all major silicon IC manufacturing companies and has also been adopted by smaller silicon device fablines looking for cost effective metrology solutions.Very recent developments in corona-Kelvin, discussed in this work, are intended for rapidly advancing wide-bandgap semiconductor technology that includes SiC, GaN, and AlGaN/GaN heterostructures.