Characterization of Gate Dielectrics with Mercury Gate MOS Current-Voltage Measurements

MOS device performance and reliability depend strongly on the quality of the gate dielectric. Metallic contamination, stoichiometry, interface properties, and substrate quality all have an influence. Gate Oxide Integrity (GOI) measurements are frequently used for monitoring oxide quality and reliability. Conventionally, testing the integrity of these gate dielectrics requires the use of prefabricated polysilicon or metal gate MOS capacitors (MOSCAPs). However, this involves short loop processing that is time-consuming and can itself affect the gate oxide quality. Therefore, a method that can monitor these factors rapidly and accurately for both production and process development is highly desirable. In this paper, a mercury gate is presented for Gate Oxide Integrity (GOI) measurements. This mercury gate is formed using a highly repeatable mercury probe Capacitance-Voltage/Charge-Voltage/Current-Voltage (CV/QV/IV) system. Several applications are discussed that show how these measurements may be used in monitoring a variety of process-induced defects. An example of the application of mercury gate Metal-Oxide-Semiconductor Current-Voltage (MOS IV) measurements for ultra-thin (less than 10 nm) oxide development is also presented.